268 PHYLU:\I XI. LEPIDOPHYTA 



which are very numerous in their sporangia, and the 

 hu'gcr ones (megaspores) which are mostly four in each 

 sporangium. These microsporangia and megasporangia 

 are intermingled in the cones. When mature the 

 microspores fall out and are blown awa}^, but it often 

 happens that the megaspores remain in the old wall of 

 the megasporangium. 



479. The gametophytes of the Club-mosses have almost 

 disappeared. When a microspore germi- 

 nates, it becomes divided into a consider- 

 able number of cells, one of which is the 

 remnant of the gametophyte (prothallium), 

 while the other cells form one large an- 

 lagineiia (game- thcrid, each iuncr cell of which produces 



tophytes, anthe- , . .,• , i 



rid, sperms, ar- blClliated SpCrmS. 



c egones, egg . ^g^^ ^^^^ mcgaspore likewise produces a 



very small but many-celled gametophyte, which pro- 

 trudes but little from the ruptured spore-wall. Upon 

 this several archegones develop. This development 

 may take place while the megaspore is still enclosed 

 in the wall of its sporangium. After fertilization the 

 egg gives rise directly to a leafy 

 plant, which emerges from the spore- 

 wall in a way to remind one very 

 forcibly of the growth of a plantlet 

 from a seed. This resemblance is 

 made greater by the hkeness of the ^^^ i 4 4._seiagineUa 

 first leaves to cotyledons. spo^esf ^^^^' ^ ^ ° ^ ^ " ^ '*• 



481. But one genus, Selaginella, 

 is known in this family. It contains many species, 

 most of which are tropical. Several species are com- 

 mon throughout the United States, and several exotic 

 species are frequently cultivated in plant-houses. 



