32 



PLANT STEUCTUEES 



by walls, or they are ccBiiocytic, as in the Siphon forms. 

 The characteristic asexual spores are zoospores, but these 

 may be wanting, as in the Conjugate forms. In addition 

 to asexual reproduction, both isogamy and heterogamy are 

 developed, and both zygotes and oospores are resting spores. 





Fig. 17. A group of Beemids, one-celled Conjugate forms, showing various pat- 

 terns, and tlie cells organized into distinct halves. — After Kerner. 



The Green Algse are of special interest in connection 

 with the evolution of higher plants, which are supposed to 

 have been derived from them. 



3. Ph^ophtce.e {Bnnvn Algce) 



28. General characters. — The Blue-green Alga? and tlie 

 Green Algae are characteristic of fresh water, but the Brown 

 Algae, or " kelps," are almost all marine, being very charac- 



