CHAPTER III. THE THALLOPHYTA. 



275 



a capillitium. When the spores germinate, the protoplasm escapes 

 and moves about, sometimes at first by means of cilia,and then, 

 losing their cilia, by amoeboid movements ; more commonly, how- 

 ever, the movements are amoeba-like from the very start. The 

 moving particles, after growing considerably, divide, the move- 

 ments in the meantime continuing. After a while, however, two 

 or more of them come together, and the mass thus formed attracts 

 other of the particles, which move toward it and unite with it, 

 forming a colony of considerable size. The colony then sooner 



or later begins to develop its fructifi- 

 cation. But before the fructifying 

 period arrives, if the weather be- 

 comes dry and the conditions are 

 not suitable for vegetative growth, 

 the plants become motionless, shrink 

 into compact and more or less 

 rounded forms, secrete a tough en- 

 closing membrane, and are then able 

 to stand desiccation. When favor- 

 able conditions for growth return, the 

 protoplasm escapes from its enclos- 

 ure and resumes its activity. 



No sexual reproduction is known 

 in these plants, for there is good 

 reason for believing that the union 

 which takes place between the amoeboid particles previous to 

 fructification, is not a sexual phenomenon, but purely a vegeta- 

 tive one analogous to that which takes place in many Fungi and 

 some Alga. 



Some of the different stages in the development of one of 

 these plants are represented in Fig. 466. Fig. 467 represents the 

 sporangia of another species. 



Fig. 467. — Sporangia of another 

 species of Myxomycetes, Arcyria in- 

 carnata. a, ripe sporangium before 

 dehiscence; b, after dehiscence and 

 the dispersion of the spores, show- 

 the net-work of the capillitium. Also 

 after De Bary. 



