180 



STUDIES IN CKYPTOGAMS 



by means of special organs, oogonia Fig. 315. o, and antheridia Fig. 

 315, a. Both of these are specially developed branches from the 

 thallus. The antheridia are nearly cylindrical, and curved toward 



the oogonia. The upper part 

 of an antheridium is cut off 

 by a cross-wall, and within 

 it numerous ciliated sperm- 

 cells are formed. These escape 

 by the ruptured apex of the 

 antheridium. The oogonia are 

 more enlarged than the an- 



315. Thread of vaueheria with oogonia 

 and antheridia. 



theridia and have a beak-like projection turned a little to one side 

 of the apex. They are separated from the thallus- 

 thread by a cross-wall, and contain a single large 

 green cell, the egg-cell. The apex of the oogonium 

 is dissolved, and through the opening the sperm-cells 

 enter. Fertilization is thus accomplished. After ferti- 

 lization the egg-cell becomes invested with a thick wall 

 and is thus converted into a resting -spore, the oospore 

 (Fig. 316), 



316. 



Ripe oospore 

 of vaueheria. 



FUNGI 



Some forms of fungi are familiar to every one. Mushrooms and 

 toadstools, with their varied forms and colors, are common in fields, 

 woods, and pastures. In every household the common moulds are 

 familiar intruders, appearing on old bread, vegetables, and even within 

 tightly sealed fruit jars, where they form a felt-like layer dusted over 

 with blue, yellow, or black powder (181). The 

 strange occurrence of these plants long mysti- 

 fied people, who thought they were produc- 

 tions of the dead matter upon which they grew, 

 but now we know that a mould, like any other 

 plant, cannot originate spontaneously ; it must 

 start from something which is analogous to a 

 seed. The "seed" in this case is a spore. The 

 term spore is applied to the minute reproduc- 

 tive bodies of all flowerless plants. A spore is 

 317. Mucor mucedo, show- a very simple structure, usually of only one 

 plant cell, whose special function is to repro- 

 duce the plant. A spore may be produced by a vegetative process 

 (growing out from the ordinary plant tissues), or it may be the re- 

 sult of a fertilization process (316). 



