Acrostichum aureum
Content
Description
Terrestrial or subaquatic fern, growing in clumps, sometimes gregariously occupying an area.
Distribution
Japan present, South Africa present, pantropical and subtropical present
Pantropical and subtropical (Japan, South Africa).
Notes
1. Small sizes, pinna apex shape and other characters formerly attributed to A. speciosum vary within the whole geographical distribution area.
2. The shape of pinna apex is apparently in accordance with frond development, the younger frond seems to have an acute apex, which in time becomes obtuse. The old individuals then bear pinnae which are more or less emarginated. Numbers of specimens with big size (big frond) are combined with acute/acuminate pinna apex, which meant that those may be big (and mature) individuals, but not old enough to show the obtuse-emarginate apex. Therefore, logically the opposite combination, small frond (body) size — meaning plant in young stage — with obtuse-emarginate apex is rarely (never?) observed. The A. aureum pinna shape types tend to occur in specimens with big size, and A. speciosum types on the specimens with smaller sizes. But overlaps occur in many cases.
3. Troll () tried to describe the shape of paraphyses of the two species and said that the A. aureum has paraphyses with protrusions, A. speciosum not. In the specimens previously identified as A. aureum, both shapes of paraphyses occur in a single sterile pinna. When the paraphyses without protrusions are abundant, the other form is sometimes difficult to observe, and the other way round. But, both shapes are definitely occurring in one specimen.
4. Trichomes on stipe. The minute, 1-3 (mostly 1) celled trichomes (hairs) were found on many specimens, but never reported before. The hairs can be found from the base of stipe up to petiolules, but the latter position is rarely observable. As the frond grows bigger, all the hairs tend to fall of; therefore the bigger specimens are always glabrous. For this reason the hairs are only found in specimens that formerly were regarded as belonging to A. speciosum. From SEM images of the stipe surface it is clear that the hairs would have been present in all individuals, gradually falling off (leaving hair scars), and eventually they have completely disappeared from the frond.
2. The shape of pinna apex is apparently in accordance with frond development, the younger frond seems to have an acute apex, which in time becomes obtuse. The old individuals then bear pinnae which are more or less emarginated. Numbers of specimens with big size (big frond) are combined with acute/acuminate pinna apex, which meant that those may be big (and mature) individuals, but not old enough to show the obtuse-emarginate apex. Therefore, logically the opposite combination, small frond (body) size — meaning plant in young stage — with obtuse-emarginate apex is rarely (never?) observed. The A. aureum pinna shape types tend to occur in specimens with big size, and A. speciosum types on the specimens with smaller sizes. But overlaps occur in many cases.
3. Troll () tried to describe the shape of paraphyses of the two species and said that the A. aureum has paraphyses with protrusions, A. speciosum not. In the specimens previously identified as A. aureum, both shapes of paraphyses occur in a single sterile pinna. When the paraphyses without protrusions are abundant, the other form is sometimes difficult to observe, and the other way round. But, both shapes are definitely occurring in one specimen.
4. Trichomes on stipe. The minute, 1-3 (mostly 1) celled trichomes (hairs) were found on many specimens, but never reported before. The hairs can be found from the base of stipe up to petiolules, but the latter position is rarely observable. As the frond grows bigger, all the hairs tend to fall of; therefore the bigger specimens are always glabrous. For this reason the hairs are only found in specimens that formerly were regarded as belonging to A. speciosum. From SEM images of the stipe surface it is clear that the hairs would have been present in all individuals, gradually falling off (leaving hair scars), and eventually they have completely disappeared from the frond.