LIFE FORM 371 



Gislen in 1930 proposed another classification to include both 

 plants and animals, the biological types referable to the plants 

 being as follows : 



I. Crustida (Crustaceous thallus) : 



(i) Encrustida or encrusting forms, e.g. Lithothamnion. 

 (2) Torida or small cushions, e.g. Rivularia. 



II. CoRALLiDA (lime skeleton more or less developed): 



(i) Dendrida or tree-like forms, e.g. Corallina. 



(2) Phyllida or leaf-like forms, e.g. Udotea. 



(3) Umbraculida or umbrella-like forms, e.g. Acetahularia. 



III. SiLViDA (no lime skeleton) : 



{a) Magnosilvida, or forms more than i dcm. high and with 

 branches more than i mm. thick. 



i) Graminida, e.g. Zoster a (a phanerogamic group). 



2) Foliida, e.g. Laminaria, 



3) Sack-form, e.g. Enter omorpha. 



4) Palm form, e.g. Lessonia. 



5) Buoy form, e.g. Nereocystis. 



6) Cord form, e.g. Himanthalia. 



7) Shrub-like form, e.g. Chordaria. 



8) Sargassum form. 



9) Caulerpa form. 



{h) Parvosilvida (small delicate forms less than i dcm. high). 



It will be seen that all these classifications are based primarily upon 

 morphological criteria and are therefore incomplete because they 

 do not take into consideration the biological requirements of the 

 algae. 



Setchell propounded a scheme in 1926 based primarily on the 

 conditions found in tropical waters, with particular reference to 

 coral reefs. For this reason the classification is restricted because it 

 would require considerable extensioa if the flora of colder waters 

 were to be included, but at the same time it is an improvement over 

 the previous schemas in that its basis is largely ecological : 



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