Tectaria pubescens

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Tectaria pubescens

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Taxonomy

The generic names Hemigramma Christ and Quercifilix Copel., cited as synonyms above, call for comment. The sterile and fertile fronds of the types of both genera are strongly dimorphous, the sterile ones having venation as in Tectaria sect. Tectaria, the fertile ones having a greatly contracted lamina with simplified venation and sporangia borne all along the veins, giving an acrostichoid appearance.

Christ established the genus Hemigramma (1907) for a Java fern originally named Hemionitis zollingeri Kurz (Tectaria zollingeri here) with the allied Philippine species (here named Tectaria hilocarpa) as a variety. Copeland (1928) added other species, two of which (from Hong Kong and Tonkin) have broader fertile pinnae in which the venation, though contracted, is normal for Tectaria sect. Tectaria; these two are not nearly related to the type of Hemigramma. All these ferns, including the type of Quercifilix, represent different modifications of fertile fronds which have evidently arisen on different evolutionary lines. The Philippine Tectaria hilocarpa hybridizes naturally with Tectaria crenata. Copeland in 1928 also included in Hemigramma the very different species here named Chlamydogramme hollrungii, not noticing its peculiar indusia.

The vein-pattern in sect. Tectaria is closely similar to that in several genera of Polypodiaceae; this appears to be a remarkable example of parallel evolution.