. Text-book of botany, morphological and physiological. Botany. EQUISETINEM. 403 portion of each protuberance remains slender, and forms the pedicel of the hex- agonal peltate scale. The outer surface of these scales is tangential to the axis of the spike; on its inner side, facing the axis, arise the sporangia, five or ten in number on each scale. In the early stages of development each single sporangium has the appearance of a small blunt multicellular wart; [an axial row of the cells grows more vigorously than the rest, and it is the terminal hypodermal cell of this row which constitutes th
. Text-book of botany, morphological and physiological. Botany. EQUISETINEM. 403 portion of each protuberance remains slender, and forms the pedicel of the hex- agonal peltate scale. The outer surface of these scales is tangential to the axis of the spike; on its inner side, facing the axis, arise the sporangia, five or ten in number on each scale. In the early stages of development each single sporangium has the appearance of a small blunt multicellular wart; [an axial row of the cells grows more vigorously than the rest, and it is the terminal hypodermal cell of this row which constitutes the archesporium. The epidermal layer divides by walls parallel to the surface, so that four layers of cells invest the archesporium, of which the two outer form the wall of the sporangium, and the two inner the tapetum]. By repeated divisions the archesporial cell produces the spore-mother-cells which be- come isolated, while of the exterior cell-layers which at first envelope them only the outermost finally remains as the wall of the sporangium. The mother-cells of the spores, connected to- gether in groups of fours or eights, float freely in a fluid which fills the sporangium and is inter- spersed with granules. The processes that take place in the mother-cells up to the time of the formation of the spores have already been de- scribed in detail in Chap. I (see Fig. 10, p. 14)1. It was there shown how the division into four of the mother-cells is preceded by an indication of a division into two, in a manner analogous to the corresponding process in Ferns. The ripe sporangium opens by a longitudinal slit on the side which faces the pedicel of the peltate scale. The very thin-walled cells of the wall have previously formed spiral thickening ridges on the dorsal, annular ones on the ventral side of the sporangium, arising, according to Duval- Jouve, in the case of E. limosum, with extra- ordinary rapidity immediately before the de- hiscence. The development of the spores of Equis
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1882
