DEVELOPMENT OF PLANTS 281 



spore mother cell, but in the Rid Algae and Rkciocarpus a con- 

 siderable growth intervenes before the spore mother cells apfx-ar 

 and the reduction of the chromosomes takes place. In other 

 words, as we ascend the scale of plant life, the formal ion oi the 

 spore mother cells and the reduction of the chromosomes is pre- 

 ceded by an ever-increasing growth of the gametospore. This 

 postponement in the formation of the spore mother cells, owing 

 to the larger and larger growth of the gametospore, will steadily 

 progress in the following studies. 



These simple liverworts, like Ricciocarpus, show very clearly 

 two phases or generations in their life history'. The thallose 



Fig. 185. Diagram of the life history of Ricciocarpus. The upix-r ix>r- 

 tion of the figure represents the sexual generation and the lower portion, 

 the asexual. The former generation begins with the formation of the spores, 

 sp, from the mother-cell and ends with the formation of the gametes, g. The 

 asexual generation begins \vith the gametospore, gm, and ends with the sjwrc 

 mother cells, sm. 



plant is the gametophyte or sexual generation because it lK»ars 

 sexual cells or gametes. The capsule is the sporophyte or asex- 

 ual generation because it can only produce spores. The gameto- 

 phyte begins with the spore and ends with the formation of the 

 gametes. The sporophyte begins with the gametospore and ends 

 with the division of the spore mother rrll (Fig. 185). It may 

 appear to you now as strange to regard the few cells of the cap- 

 sule, the majority of which become spore mother cells, as a plant. 

 But w«^ ^all directly see this microscoi)ic plant assuming larger 

 proT[89. Diagl? a result of its better nourishment and the stimuli 

 t- buds or^posed. It will form a larger mti.1 I.nvcr numU^r 



