CHAPTER XIX 



BRYOPHYTES (MOSS PLANTS) 



105. Summary from Thallophytes. — Before considering the 

 second great division of plants it is well to recall the most 

 important facts connected with the Thallophytes, those 

 things which may be regarded as the contribution of the 

 Thallophytes to the evolution of the plant kingdom, and 

 which are in the background when one enters the region of 

 the Bryopliytes. 



(1) Iiij-reaaituj complexity vf tin' hodif. — Beginning with 

 single isolated cells, the plant body attains considerable 

 complexity, in the form of simple or branching filaments, 

 coU-plates, and cell-masses. 



(3) Ajipeayinire of s^jorex. — The setting apart of repro- 

 ductive cells, known as spores, as distinct from nutritive 

 cells, and of reproductive organs to organize these spores, 

 represents the first important differentiation of the plant 

 body into niitritive and rej^roductive regions. 



(3) Differentiation of xjiorea. — After the introduction of 

 spores they become different in their mode of origin, but 

 not in their powe-r. The asexual spore, ordinarily formed 

 by cell division, is followed by the appearance of the sexual 

 spore, formed by cell union, the act of cell union being 

 known as the sexual process. 



(4) Diferentiation of gametes. — At the first appearance 

 of sex the sexual cells or gametes are alike, but after- 

 ward they become different in size and activity, the large 

 passive one being called the egg, the small active one the 



