102 STUDY OF COMMON PLANTS. 



Vaucheria is reproduced by oospores and also by swarm- 

 spores. 1 



I. By oospores. These are easily obtained from speci- 

 mens growing on damp earth, and may be satisfactorily 

 studied both in living and alcoholic material. Using first 

 the low power of the compound microscope, observe 



1. The organs of reproduction generally growing close 



together. 



a. The cylindrical anther idium. 



b. The obliquely oval oogonia, commonly two with 



each antheridium. Draw. 



2. The structure of both antheridium and oogonium. 



Examine this more in detail, using the high power, 

 and, if practicable, having fresh material. 



a. Early stages of development may be found. If 



these are met with, make a series of sketches, 

 showing both oogonia and antheridia at dif- 

 ferent periods. 



b. The process of fertilization should be observed, if 



possible. It will probably involve the outlay 

 of considerable time, yet there are few plants 

 in which the process can be more satisfactorily 

 followed. It is even more striking in CEdogo- 

 nium, a plant closely related to Vaucheria, on 

 account of the large size of the antherozoids. 2 



II. By swarm-spores. These cannot always be had 

 when wanted, but are unusually large, and on account of 



1 For other forms of vegetative reproduction, cf. Goebel, Outlines of 

 Classification and Special Morphology, p. 32. 



2 For an account of the process and further directions, cf. Strasburger, 

 Practical Botany, pp. 252-254. 



