146 EVOLUTION OF PLANTS 



reduced to a single vegetative cell, and a single anthe- 

 ridium in which are developed biciliate spermatozoids 

 like those of Lycopodium (D)* 



In both Lycopodium and Selaginella, the stem of the 

 sporophyte is long and extensively branched, while the 

 leaves are small and moss-like. The tissues, especially 

 the vascular bundles, are not unlike those of the ferns. 

 Sometimes the stem and root grow from a single apical 

 cell, sometimes a group of initial cells is present, but 

 even when there is a single apical cell, it never shows the 

 almost mathematical regularity in its divisions found in 

 the leptosporangiate ferns or in Equisetum. 



The sporangia in both Lycopodium and Selaginella 

 are borne singly, either upon the inner face of the 

 leaves, or upon the axis just above a leaf. They are 

 kidney-shaped capsules, which open by a longitudinal 

 cleft (Fig. 87, B). The sporophylls are usually 

 crowded together into a cone or strobilus, somewhat 

 as in Equisetum. In Lycopodium all the sporangia are 

 alike, but in Selaginella the oldest one (or ones), at the 

 base of the cone, matures but four spores (macrospores), 

 which are very much larger than the numerous micro- 

 spores produced in the upper sporangia (Fig. 38, B). 

 The development of the two kinds of spores is the same 

 up to the point where each mother-cell divides into the 

 four spores. In the microsporangia all the spores de- 

 velop, but in the macrosporangium only one tetrad comes 

 to maturity, the others serving simply as food for the 

 developing macrospores. These begin to germinate 

 within the sporangium, and besfdes using up the other 

 spore-tetrads as food, are nourished from the sporophyte 

 through the cells of the sporangium- wall, which re- 



