. The Eusporangiatae; the comparative morphology of the Ophioglossaceae and Marattiaceae. Ophioglossaceae; Marattiaceae. THE OLDER SPOROPHYTE 205 top of which is expanded so that it overarches the synangia. This ridge in section appears T-shape. Whether this growth of leaf tissue between the synangia in Dancea is to be considered as an indusium may be questioned. It appears to be very similar in structure to the oblong cavity or fovea, within which is sunk the not very dissimilar synangium of Isoetes (fig. 189, B). THE SPORANGIUM OF THE MARATTIACE^ In Angtopterts and Archangtopteris there are
. The Eusporangiatae; the comparative morphology of the Ophioglossaceae and Marattiaceae. Ophioglossaceae; Marattiaceae. THE OLDER SPOROPHYTE 205 top of which is expanded so that it overarches the synangia. This ridge in section appears T-shape. Whether this growth of leaf tissue between the synangia in Dancea is to be considered as an indusium may be questioned. It appears to be very similar in structure to the oblong cavity or fovea, within which is sunk the not very dissimilar synangium of Isoetes (fig. 189, B). THE SPORANGIUM OF THE MARATTIACE^ In Angtopterts and Archangtopteris there are formed separate sporangia not very unlike those found in Botrychium or Helminthostachys, but in all the other genera the sporangia are fused into a synangium which might be compared with the spike of Ophioglossum. The synangium in DaruBa stmplicifolta may reach a length of over 3 centimeters and contain upward of 100 loculi. The first study of the development was made upon Marattia by Luerssen (Luerssen 3). According to his statement, the differenti- ation of the synangium begins while the leaf is still very small and rolled up between the stip- ules. The tissue about a vein begins to develop into an elevated cushion following the vein. Upon this receptacle there are devel- oped two parallel ridges of tissue, separated by a cleft. These two ridges later grow upward and meet above, so that their edges completely close up the cleft, which no longer shows from the outside. In each half of this syn- angium, very much as is the case in the sporangial spike of Ophio- glossum, there are developed sep- arate archesporial groups corre- sponding to the separate cham- bers that are found in the fully developed synangium. Luerssen states that the whole process takes about six months for its completion (fig. 186). In Angiopteris (fig. 187) the development of the sporangium begins at a much later period, when the leaf is almost completely developed. The sporangia here are arranged in an oblo
Size: 1608px × 1553px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
