PROTOPHYTA. 



123 



is presented by some of the members of this group, viz. by 

 the formation of spores (Fig. 233). 



156. As representatives of this division (Protophyta), 

 the Myxomycetes, or Slime-Moulds, are the most re- 

 markablck During their growing, or vegetative stage, they 

 consist of a homogeneous mass of colored (but never green) 

 protoplasm, which has received the name of plasmodium. 

 There is no cell-wall ; there is a streaming or circulation in 

 the mass of protoplasm, and the latter can, by constant 

 change of form, move slowly around on the damp decaying 

 ■wood, or vegetable mould, 

 ■where these plants are 

 often to be met with. In 

 their vegetative state they 

 are so much like the 

 lower animals (Monera) 

 that they were, for a long 

 time, considered as belong- 

 ing to the animal king- 

 dom. If they are brought ^^^ 

 to rest by absence of proper moisture and temperature, they 

 become changed into rounded masses, and secrete a cellu- 

 lose wall. This is called the sclerotium stage. Upon re- 

 turn of suitable conditions, the plasmodium form is again 

 assumed. The reproductive stage is also one of rest ; the 

 mass becomes compact, heaped up into definite shapes (Fig. 

 233, J) surrounded by cellulose; the protoplasm within 

 becomes separated into multitudes of spores (Fig. 233, V), 

 which, in many species, are commingled with an irregular 

 net-work of (often ornamented) filaments, called the capil- 

 litium (Fig. 233, III, IV). Under proper conditions the 



Fig. 233. Arcyrta. fontiformis.s, Slime-Mould; c, capillitium ; j;!, sporangium; 

 /, plant, natural size; //and ///, magnified sixteen diameters; IV, capillitium; 

 V, spores, more highly magnified. 



