Mar., 1922 classification of plants 133 



Class, SiPHOXE.E. Higher Tube Algje. 200 species. 



■ I. Sexual reproduction unknown or isogamous. 



A. Small globular terrestrial plants with branched rhizoids penetrating the 

 ground; zoospores with cilia of unequal lengths. 



Botrydiales. Botr\'diaceas. 



B. Mostly large marine or sometimes endophytic algae; zoospores if present 

 not wnth unequal cilia. Bryopsidales. Derbesiacea^, Bryopsidaceae, 

 Caulerpace^, PhvUosiphonaceEe, Codiaceae. 



XL Se.xual reproduction bV highly specialized stationary eggs and motile sperm- 

 atozoids; thallus tubular, branched or unbranched; growing in fresh or 

 brackish water or on moist soil. Vaucheriales. Vaucheriaceaj. 



Class, CoNFERVE.^. Confervas. 650 species. 



I. Isogamous, or the free-swimming gametes sometimes of unequal size. 



A. Thallus unbranched. 



1. Chloroplasts reticulate, without pyrenoids; fresh water plants. 

 Microsporales. Microsporaceae. 



2. Chloroplasts central or parietal, with one or more pyrenoids. _ 



a. Chloroplast single, central, stellate, with one pyrenoid; no 

 zoospores known; aerial in habit. Prasiolales. Prasiolaces. 



b. Chloroplast parietal, with one to many pyrenoids. 



(a) Unbranched filaments; chloroplasts with one to many 

 pyrenoids. Ulotrichales. Ulotrichaceae, Tribonemacese. 



(b) Thallus expanded, a 1-2-layered plane or tube; chloroplast 

 single, with 1 pyrenoid; mostly marine. Ulvales. Ulvaceae. 



B. Thallus filamentous, branched, usually abundantly so, the branches 

 often attenuated or hair-like tips. Chaetophorales. Chaetophoraceae, 

 Trentepohliaceae, Harposteiraceae. 



II. Heterogamous, the egg stationary in the oogonium; sometimes with a prim- 

 itive alternation of generations. 



A. Oogonium not developing a cortical layer after fertilization. Oedogoniales. 

 Cylindrocapsaceae, Oedogoniaceas. 



B. Oogonium with a trichogyne-like tip, covered after fertilization by a 

 cortical layer; thallus disk-like or cushion-like. Coleochaetales. 

 Coleochaetacese. 



Phylum, Phaeophyta. Brown Algae. 



I. Zoospores present; sexual reproduction by motile, biciliate gametes produced 

 ia external gametangia, occasionally by heterogametes, and in extreme cases 

 by nonmotile eggs. Class, Phaeospor.e. Kelps. 550 species. 



A. Zoospores and isogametes similar and motile. 



1. Frond various, simple or branched, but never differentiated w4th 

 definite root-like and leaf-like parts. Ectocarpales. Ectocarpacese. 



2. Frond large, leather-like, usually stalked, differentiated with root- 

 like and leaf-like parts; with zoospores only. The largest marine 

 plants. Laminariales. Laminariacege. Giant Kelps. 



B. Zoospores and heterogametes dissimilar. 



1. Gametes large and small, but both motile. Cutleriales. Cutleriaceas. 



2. Gametes consisting of small active spermatozoids and nonmotile 

 eggs; frond filiform. Tilopteridales. Tilopteridaceae. 



II. Zoospores absent; sexual reproduction by means of motile sperms and non- 

 motile eggs which are discharged from the oogonium; nonsexual reproduction 

 absent or by means of nonmotile spores. 



A. Sperms biciliate; without nonsexual spores; gametangia in sunken con- 

 ceptacles. Class, Cyclospor.^. Rockweeds. 350 species. One order 

 Fucales. Durvillaeaceae, Himanthaliaceag, Fucaceae, Sargassaceae. 



B. Sperms with one flagellum; nonsexual spores nonmotile; reproductive 

 organs external; with a regular alternation of se.xual and nonsexual 

 generations. Class, Dictyote.e. 130 species. One Order, Dictyotales. 

 Dictyotaceae. 



