A MANUAL OF BOTANY 107 



for oval or globular bodies with green filaments grow- 

 ing from one or both ends. These structures, if found, are 

 (jerminatimj spores, (i)robably zoospores) showing how the 

 plant grows from these reproductive structures. 



Rhizoids. In the land material mentioned above, seek for 

 root-like branched structures. If found, what color have 

 they? What might be the use of the same? Recall where 

 the plant grows. Seek for the same in the water material. 

 These structures are rhizoids. 



Sexual reproduction. On either kind of material, seek for 

 short branches, api)roximately at right angles to the filament, 

 but differing in arrangement of the two coni})onent parts in 

 the two kinds under consideration. In the greenhouse form 

 there are two branches, adjacent, one round or oval, and the 

 other cylindrical and strongly curved, which finally unites 

 its tip with the spherical body. This latter body is the 

 oogonium containing the female gamete (uniting cell) or 

 oosphere and the curved body is the antheridium contain- 

 ing the male gametes. Observe whether these structures 

 are marked off from the main filament by a cell wall or not. 

 What color has each? In the mature antheridium, find 

 some that have lost their contents. What has become of 

 the same? The result of this reproductive process, by the 

 union of the contents of two cells, is a sexual spore, or 

 oospore which is a structure th<at commonly remains dor- 

 mant for some time (resting spore) before germinating. 

 What use could they serve in the plant history ? Observe 

 the thickness of the cell wall of the oospore. Why is the 

 wall so thick? If the form is the one growing in water, 

 both gametes organs are found on the same branch, and 

 there are several oogonia. 



Drawings. ISIake the following drawings if the material 

 will permit : — 



1. A complete filament with its branches and growing 

 tips. 



