268 PHYLUM XI. LEPIDOPHYTA 
which are very numerous in their sporangia, and the 
larger 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 away, 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), 
i a hig while the other cells form one large an- 
laginella (game- therid, each inner cell of which produces 
rt Ssperms, ar- biciliated sperms. 
cheponennen). 2 P . ° 
480. The megaspore 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 8 "sf 
made greater by the likeness of the (144 ~Siclaginill 
first leaves to cotyledons. (sporophyte, sporangia, 
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. 
