248 



PLANT STl'DIES 



by walls, or they are ccenocytic, 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. 







Frr,. '^10. A group of Desmids, one-celled Conjugate forms, showing various pat- 

 terns, and the cells organized into distinct liaKcs. — After Kerner. 



The rjroen Algi>^ are of special interest in connection 

 with the evolution of higher plants, which are supposed to 

 have been derived from them. 



3. Pii,i:oPHTCE.E {Braini Alfjcv) 



KiO. General characters, — The Illnc-green Algtp and the 

 (ireen Algffi arc charticteristic of fresh Avater, but the Brown 

 Algffi, or " kelps," arc almost all marine, being very charac- 



