Flowers. 



203 



m 



does not differ from a foliage leaf in appearance. One 

 kind of sporangium contains relatively small spores termed 

 microspores (Fig. 121) which on germination give rise to a 

 rudimentary plant body called prothallium, bearing sperm 

 cells ; and the other sort of sporangium contains relatively 

 large spores, the macro- 

 spores (Fig. 12 1), which 

 on germination produce a 

 prothallium bearing egg 

 cells. The sporangium 

 containing macrospores 

 is termed macrosporan- 

 gium, and the sporophyll 

 subtending it macrosporo- 

 phyll, while the corre- 

 sponding parts relating to 

 the microspores are called 

 micro sporangium and mi- 

 crosporophyll. 



Now, in a flower, since 

 the pollen grain produces 

 the sperm, it must be a microspore, the anther a microspo- 

 rangium, and the entire stamen a modified microsporophyll. 

 The large cell in the ovule (termed embryo sac} which pro- 

 duces the egg must be the macrospore, and the ovule the 

 macrosporangium, while the pistil evidently corresponds to 

 a macrosporophyll with the edges infolded and grown 

 together forming an inclosed chamber. Each sporophyll 

 taking part in the formation of a pistil is called a carpel. 

 Or the pistil may be composed of more than one sporophyll 

 united, as indicated by the number of styles, stigmas, or 

 groups or rows of ovules. When composed of a single 

 sporophyll or carpel the pistil is said to be simple, when of 



FIG. 121. 



i, Selaginella. Toward the summit of the 

 plant the leaves are more pointed, and they 

 become aggregated into a cone-like group 

 at the apex. 2, Microsporangium, m, 

 discharging microspores ; n, macrosporan- 

 gium containing macrospores. After 

 STRASBURGER. 



