CRYPTOGAMS 



The Mosses as well as the Pteridophytes multiply also asexually 

 by means of walled SPORES adapted for dissemination through the air. 

 These two modes of reproduction, sexual and asexual, occur in 

 regular alternation, and are confined each to a sharply distinct 

 generation ; a sexual, provided with sexual organs, and an asexual, 

 which produces spores. The sexual generation arises from the spore ; 

 the asexual from the fertilised egg. This alternation of genera- 

 tions is characteristic of all Archegcmiatae. 



In the development of the sexual generation, the unicellular spore 



*^.> 



A 





Ji 



Fig. 312. — Funaria hygrometrica. A, Germinating spore ; ex, exine ; B, protonema ; Jen, buds ; 

 r, rhizoids ; s, spore. (After MUller-Thurgau ; magnified.) 



on germinating ruptures its outer coat or exine, and gives rise to a 

 germ-tube. In the case of the Hepaticae, the formation of the plant 

 at once commences, but in most of the Musci a PROTONEMA is 

 first produced, which resembles in structure the filaments of Confer- 

 void Algae, and is composed of cells containing chlorophyll (Fig. 

 312, A, B). The green, filamentous protonema gives rise to branched, 

 colourless rhizoids (r), which penetrate the substratum. The Moss- 

 plants arise from buds developed on the protonema at the base 

 of the branches. Protonema and Moss-plant together represent the 

 sexual generation. Many Liverworts possess a thallus consisting of 

 dichotomously branching lobes, which is attached to the substratum 

 at its base or on the under side by means of rhizoids, thus repeat- 

 ing the vegetative structure of many Algae (cf. Fig. 8 with Fig. 9, 

 p. 1 3). In other Hepaticae, on the other hand, and in all the Musci, 

 there exists a distinct differentiation into stem and leaves (Fig. 323). 

 In no instance, however, are true roots formed or a tissue of cells 



