236 FOUNDATIONS OF BOTANY 



Asexually produced spores are sometimes formed, each 

 by the condensation of the protoplasm of a single cell, as 

 shown in Fig. 174, E. They are also formed by the con- 

 tents of spore-cases breaking up into many spores (Fig. 

 173, B\ Fig. 210, D). Spores are sometimes produced by 

 the spontaneous division of a mass of protoplasm into a 

 small definite number of segments (Fig. 188, t). Spores 

 which have the power of moving (swimming) freely are 

 known as zoo spores (Fig. 179, B). 



Sexually produced spores are formed in many ways. 

 One of the simplest modes is that shown in Fig. 178, 

 resulting in zygospores. Other methods are illustrated in 

 Figs. 185 and 187. 1 



THE STUDY OF SLIME MOULDS 2 



260, Occurrence. Slime moulds occur in greenhouses, in tan- 

 yards, or on old logs arid decaying leaves in woods. They may be 

 cultivated in the laboratory. 



They have been described in their vegetative condition on page 179. 



261, Examination with the Magnifying Glass. Stemonitis is one 

 of the most available genera to illustrate the fruiting of slime moulds. 

 At maturity the motile protoplasm of the vegetative stage quickly 

 transforms itself into numerous sporangia or spore-cases with dust- 

 like spores. With the naked eye and with a magnifying glass note 

 the color, form, and feathery appearance of the spore-case of Stemo- 

 nitis. The outer wall disappears at an early stage, leaving only an 

 inner structure and spores. Sketch the general outline under a 

 magnifying glass. 



262, Examination with the Microscope. With a low power of 

 the microscope sketch the network of branching hairs which com- 

 pose the structure of the sporangium. Note the presence or absence 



1 See Vine's Student's Text-Book of Botany, pp. 68-71. 



2 This should logically precede Sect. 258. 



