STUDIES IN CRYPTOGAMS 



187 



The afitheridia, bearing sperm-cells, and the oogonia, each bearing 

 eight egg-cells, are sunken in pits or conceptacles. These pits 

 are aggregated in the swollen lighter coloured tips of some of the 

 branches {s, s. Fig. 269). The egg-cells and sperm-cells escape 

 from the pits and fertilization takes place in the water. The 

 matured eggs, or spores, reproduce the fucus plant directly. 



Fio. 269. — Fucus. Fruiting 

 branches at s, s. On the 

 stem are two air-bladders. 



Fig. 270. — NlTELLA. 



Nitella. — This is a large branched and specialized fresh-water 

 alga found in tufts attached to the bottom in shallow ponds (Fig. 

 2 70) . Between the whorls of branches are long internodes consisting 

 of a single cylindrical cell, which is one of thedargest cells known in 

 vegetable tissue. Under the microscope the walls of this cell are 

 found to be lined with a layer of small stationary chloroplastids, 



within which layer the protoplasm, in favourable circumstances, 



will be found in motion, moving up one side and down the other 

 (in rotation). Note the clear streak up the side of the cell and its 

 relation to the moving current. 



Fungi 



Some forms of fungi are familiar to every one- Mushrooms 

 and toadstools, with their varied forms and colours^ are common 

 iu 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. The 

 strange occurrence of these plants long mystified people, who 



