THE ALGiE 227 



covered with a bell-glass. Examine specimens on earth and in water 

 with a magnifying glass and note : 



(a) The general appearance of the felted mass of plants. 



(ft) The position of the growing filaments with reference to light. 

 This is to be looked for only in specimens left long undisturbed in 

 a good light. 



(c) The mode of branching. 



(d) The rhizoids or rooWike extensions of filaments into the earth. 

 These are best shown by washing away the earth with a carefully 

 managed stream of water from a wash bottle. 



291. Minute Structure. — Blount in water some filaments that have 

 grown many days in water, examine with m.p., then with h.p., and note : 



(a) Their varying diameter and the details of the branching. 



(ft) The presence or absence of cross-partitions. 



(c) The form and size of the chlorophyll bodies. 



If stained preparations mounted in balsam are available, study 

 them with h.p. and note : 



(c?) The very numerous nuclei. Make drawings to show the 

 points (a), (ft), and (c). 



292. Reproduction. 



I. Asexual 



"With m.p. examine plants that have been growing in water in a 

 sunny place for a week or moi-e.-' Look for : 



(a) The formation of transverse partitions near the tips of 

 branches. The end of the branch thus becomes a spore-case. 



(ft) The formation in each spore-case of a roundish, ciliated com- 

 pound zoospore. 



(c) Zoospores escaping or swimming about among the filaments. 



(d) ZoosiJores beginning to grow into new plants. 



> 



II. Sexual 



In the same kind of material studied in I, look for paired, unlike 

 organs occurring on the sides of some filaments (Fig. 157, B, C). Kote ; 



(a) The shape, size, and structure of the smaller organ. It is an 

 antlieridium, producing very minute, ciliated sperms. 



1 For culture directions to secure fruiting Vaucheria and zoospores see 

 Bergen and Davis' Field and Laboratory Manual, pp. 95, 211, 212. 



