320 



THALLOPHYTES 



Kelps that much potassium for fertiUzers is obtained (Fig. £75). 

 Although the Kelps have massive and complex plant bodies, 

 their reproduction, so far as known, is not so complete as that of 

 some Green Algae. Their reproduction is sexual and the small 

 ciliated gametes are borne in special cells which occur in patches 



Fig. 275. — Harvesting Kelp on the Pacific Coast. From Report 100, 

 U. S. Dept. of Agriculture. 



on the surfaces of the leaf-like branches. The zygospore develops 

 a new plant directly. 



Ectocarpus. — This form {Fig. 276), although belonging to the 

 same order, contrasts strikingly in size with the Kelps, for it is a 

 slender filamentous form not much larger than some of the Green 

 Algae. This form also shows some interesting features in connec- 

 tion with reproduction which is effected through the production 

 of both zoospores and gametes. 



The zoospores are produced in certain cells which become trans- 

 formed into sporangia. In forming a sporangium, a single cell 

 within the filament or at the end of a branch usually enlarges 

 and its protoplasm divides up into zoospores. The zoospores 

 bear their cilia laterally and not terminally as in the Green 

 Algae, but function in the same way by growing directly into 

 new plants. 



