Bolbitis
Distribution
Africa present, America present, Asia present, Asia-Tropical, Australasia: Queensland (Queensland present), Madagascar present, Pacific present, Pantropic present
Pantropic. In my monograph (l.c.) I recognized 44 species arranged in 10 series (of which only ser. Bolbitianae is pantropic): Africa incl. Madagascar: 9 spp., America: 14 spp., Asia and the Pacific: 21 spp. of which 12 in Malesia, Australia (Queensland): 3 spp.
Morphology
The morphology, in particular of the Indian species, has been studied by Nayar c.s. (for references see ). In my monograph an elaborate treatment of the morphology and anatomy of all species is included to which the reader is referred for details.
The rhizome of some species bears ± conspicuous buds situated on the posterior side of the leaf-bases; they may develop into accessory branches. The stele is a dorsiventral dictyostele with wide overlapping leaf-gaps. The traces running into the buds or the accessory branch traces are situated at the posterior side of the two lateral leaf-gaps only, and are formed in association with root traces and leaf traces in an obviously characteristic arrangement.
Aerophores are part of the fronds but are continuous on the rhizome for some length. On the rhizomes of Iiving material they show much variation in shape and size.
The venation pattern provides important characteristics for the discrimination of taxa. In all the species the secondary veins run parallel; typical differences are therefore expressed by the tertiary etc. veins only. See , . The venation in the pinnate fronds is anadromic.
Within the genus different types of venation occur. Veins are free in ser. Egenolfianae. In ser. Hetero- clitae and ser. Quoyanae the pattern is sagenioid; the veins anastomosing in a reticulate pattern, with ± isodiametric or elongate, angulate areoles, and generally without recurrent included free veins. In ser. Bolbitianae the veins anastomose to form a costal areole and one to many smaller distal ones, the veins near the margin running ± parallel, the areoles with or without excurrent included free veins.
A so-called irregular venation, i.e. a venation in which the arrangements of the veins in the areas included by the secondary veins are markedly different, is often (not always!) present in alloploids, hybrids, and in crossings between cytotypes of one species.
The morphological evidence as given in my monograph indicates that divergent evolution in ferns with a sagenioid venation — the condition which I regard to represent the original condition in the genus — may lead to species having either a free venation or a venation with several types of included free, ex- and/or recurrent veins.
All species have bulbils subterminally (or terminally) on the sterile (and fertile) fronds. Bulbils are ± globular, persistent structures, situated adaxially; they are covered with scales similar to those on the rhizome. Development into mature plants occurs when the apex of the mother leaf strikes the ground; under humid conditions bulbils may develop into small plants on the erect lamina. Plants grown from bulbils stay connected with the mother plant for some time ('Walking ferns').
The shape of ths fertile segments is usually about the same (though much contracted) as that of the sterile ones. The margin of the segments often lack the prominent marginal projections found in the sterile material; bulbils are less prominent or even absent. Fronds that are in part fertile and in part sterile — so-called intermediate fronds — do not rarely occur and show much variation as to the sporangial arrangement, also in one species.
The venation pattern of the fertile segments is similar to that in the sterile ones; free included veins and small areoles are however less frequent or even absent. Nayar c.s. (see Kaur, l.c.) reported a special kind of venation pattern occurring in the fertile fronds of the present genus; this is incorrect.
Insertion of the sporangia is variable; in some species the sporangia are situated all over the lower surface, in other species they are present on the veins only; also both conditions may be present in one species. Sporangia are formed in dense masses. In spite of the basipetal development of the fertile frond, sporangia of all parts of the frond reach maturity at the same time.
Spores as seen with the light microscope are monolete, biconvex, and provided with a variously shaped brown perispore. The exospore is thin, structurally not differentiated, and shows a short leasura. The perispore as seen from cross-sections studied with the electron microscope () is composed of two more or less distinct elements, of which the outer perispore can also be recognized with the light microscope. Using properties of the (outer) perispore, three types of spores can be recognized with the light microscope. In B. appendiculata the perispore is reticulate and cristate. A smooth and undulate perispore is a characteristic of ser. Bolbitianae. All other species have a smooth, cristate-undulate or cristate perispore. Although some are characterized by either a cristate or a cristate-undulate perispore, the spores of several other species display both types of perispore as well as the intermediates.
The rhizome of some species bears ± conspicuous buds situated on the posterior side of the leaf-bases; they may develop into accessory branches. The stele is a dorsiventral dictyostele with wide overlapping leaf-gaps. The traces running into the buds or the accessory branch traces are situated at the posterior side of the two lateral leaf-gaps only, and are formed in association with root traces and leaf traces in an obviously characteristic arrangement.
Aerophores are part of the fronds but are continuous on the rhizome for some length. On the rhizomes of Iiving material they show much variation in shape and size.
The venation pattern provides important characteristics for the discrimination of taxa. In all the species the secondary veins run parallel; typical differences are therefore expressed by the tertiary etc. veins only. See , . The venation in the pinnate fronds is anadromic.
Within the genus different types of venation occur. Veins are free in ser. Egenolfianae. In ser. Hetero- clitae and ser. Quoyanae the pattern is sagenioid; the veins anastomosing in a reticulate pattern, with ± isodiametric or elongate, angulate areoles, and generally without recurrent included free veins. In ser. Bolbitianae the veins anastomose to form a costal areole and one to many smaller distal ones, the veins near the margin running ± parallel, the areoles with or without excurrent included free veins.
A so-called irregular venation, i.e. a venation in which the arrangements of the veins in the areas included by the secondary veins are markedly different, is often (not always!) present in alloploids, hybrids, and in crossings between cytotypes of one species.
The morphological evidence as given in my monograph indicates that divergent evolution in ferns with a sagenioid venation — the condition which I regard to represent the original condition in the genus — may lead to species having either a free venation or a venation with several types of included free, ex- and/or recurrent veins.
All species have bulbils subterminally (or terminally) on the sterile (and fertile) fronds. Bulbils are ± globular, persistent structures, situated adaxially; they are covered with scales similar to those on the rhizome. Development into mature plants occurs when the apex of the mother leaf strikes the ground; under humid conditions bulbils may develop into small plants on the erect lamina. Plants grown from bulbils stay connected with the mother plant for some time ('Walking ferns').
The shape of ths fertile segments is usually about the same (though much contracted) as that of the sterile ones. The margin of the segments often lack the prominent marginal projections found in the sterile material; bulbils are less prominent or even absent. Fronds that are in part fertile and in part sterile — so-called intermediate fronds — do not rarely occur and show much variation as to the sporangial arrangement, also in one species.
The venation pattern of the fertile segments is similar to that in the sterile ones; free included veins and small areoles are however less frequent or even absent. Nayar c.s. (see Kaur, l.c.) reported a special kind of venation pattern occurring in the fertile fronds of the present genus; this is incorrect.
Insertion of the sporangia is variable; in some species the sporangia are situated all over the lower surface, in other species they are present on the veins only; also both conditions may be present in one species. Sporangia are formed in dense masses. In spite of the basipetal development of the fertile frond, sporangia of all parts of the frond reach maturity at the same time.
Spores as seen with the light microscope are monolete, biconvex, and provided with a variously shaped brown perispore. The exospore is thin, structurally not differentiated, and shows a short leasura. The perispore as seen from cross-sections studied with the electron microscope () is composed of two more or less distinct elements, of which the outer perispore can also be recognized with the light microscope. Using properties of the (outer) perispore, three types of spores can be recognized with the light microscope. In B. appendiculata the perispore is reticulate and cristate. A smooth and undulate perispore is a characteristic of ser. Bolbitianae. All other species have a smooth, cristate-undulate or cristate perispore. Although some are characterized by either a cristate or a cristate-undulate perispore, the spores of several other species display both types of perispore as well as the intermediates.
Taxonomy
The genus Bolbitis was founded by Schott () for a part of Acrostichum with a creeping rhizome and anastomosing veins. At the same time (l.c. ad 1.16) he accommodated the Asian species with free veins in Egenolfia, keeping the American free-veined species separate in Polybotrya. Presl () and Fee () referred the species to several different genera whereas Hooker () and Baker () merged all acrostichoids again in Acrostichum. In spite of J. Smith () who reinstated Egenolfia, Christ () and Diels () referred all the free-veined species again to Polybotrya, those with anastomosing veins to the heterogeneous Gymnopteris. Christensen () recognized Egenolfia, including the other species in an assemblage he called Leptochilus. Copeland () attempted to clear up the heterogeneities called Gymnopteris by Diels and Leptochilus by Christensen. He referred the Old World species to Campium in which he included a number of unrelated ferns as well. Ching () monographed Egenolfia. He later () reinstated Bolbitis and largely delimited the genus as presented in my book. Iwatsuki () studied the Japanese species and was the first to unite Egenolfia and Bolbitis. The emended genus he divided into 4 sections. In my monograph most of the species are accommodated in 10 series (4 in Asia all except ser. Bolbitianae endemic), whereas several species of hybrid origin are separately ranked as species incertae sedis.
Cytology
The haploid chromosome number of a considerable number of taxa as listed in my monograph was either 41 or 82. One species (B. sinuata) showed a weak indication of aneuploidy. In ser. Bolbitianae and ser. Egenolfianae only diploids were found. Of 20 specimens belonging to the 4 Malesian species of ser. Heteroclitae and ser. Quoyanae, 12 were diploids and 8 (auto)triploids; this obscured the delimitation of species of these two series in the past. Thus far apogamy has not been reported for the genus.
Notes
The treatment of the 12 recognized species is followed by the record of 5 hybrids and 2 dubious species. Of the latter two categories only those have been inserted in the key which were collected in more than one locality. Their numbers are preceded by H and D respectively.
The synonymy has been restricted to those names which were used for Malesian taxa. No types are cited because they seem not useful for botanists Consulting this Flora. For full synonymy and types see my monograph.
So-called intermediate fronds, dwarfs and aberrant specimens are generally not considered in the des- criptions.
The term segment is used for a portion of the lamina that has an axis and is not a pinna. Of the (central) segments the index (length/width ratio) is generally given.
The number of pinnae given refers to the total number of pinnae to a frond.
Caudate apices of pinnae are not included in the measures given for the length of the pinnae.
Primordia of bulbils can be traced when the sterile fronds are examined in transmitted light. They appear as small knobs terminally or subterminally.
The costa of the pinna and the simple lamina are termed the primary vein; the pinnately arranged lateral veins are designated as the secondary veins.
Chromosome numbers given are taken from the list supplied in my monograph.
The key to the species is based on characters of the sterile fronds, and sometimes on those of the spores.
Identification will be possible for most of the material using a good hand lens and preferably also a source of transmitted light to study the venation pattern.
The synonymy has been restricted to those names which were used for Malesian taxa. No types are cited because they seem not useful for botanists Consulting this Flora. For full synonymy and types see my monograph.
So-called intermediate fronds, dwarfs and aberrant specimens are generally not considered in the des- criptions.
The term segment is used for a portion of the lamina that has an axis and is not a pinna. Of the (central) segments the index (length/width ratio) is generally given.
The number of pinnae given refers to the total number of pinnae to a frond.
Caudate apices of pinnae are not included in the measures given for the length of the pinnae.
Primordia of bulbils can be traced when the sterile fronds are examined in transmitted light. They appear as small knobs terminally or subterminally.
The costa of the pinna and the simple lamina are termed the primary vein; the pinnately arranged lateral veins are designated as the secondary veins.
Chromosome numbers given are taken from the list supplied in my monograph.
The key to the species is based on characters of the sterile fronds, and sometimes on those of the spores.
Identification will be possible for most of the material using a good hand lens and preferably also a source of transmitted light to study the venation pattern.
Citation
Copel. 1960: Fern Fl. Philip.: 254
Copel. 1960: Fern Fl. Philip.: 265
Copel. 1947: Gen. Fil.: 115
Backer & Posth. 1939: Varenfl. Java: 80
Schott 1939: Varenfl. Java: 84
C. Chr. 1934: Ind. Fil.: 102
Hennipman 1977: p. 123. – In: Leid. Bot. Ser.: with full synonymy.
Holttum 1954: Ferns Malaya: 461
Backer & Posth. 1933 – In: Nat. Tijd. N. I.: 152
v.A.v.R. 1908: Handb. Mal. Ferns: 722
Copel. 1928 – In: Philip. J. Sc.: 341
Holttum 1954: Ferns Malaya: 459
Backer & Posth. 1933 – In: Nat. Tijd. N. I.: 157