440 THE ALGAE 



(i) Graminida, e.g. Zostera (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. 



(b) 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 extension if the flora of colder waters 

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

 the previous schemes in that its basis is largely ecological : 



Heliophobes : 



(i) Pholadophytes. Forms nesding into hollows and avoiding 

 much light. 



(2) Skiarophytes. Forms growing under rocks or in their shade. 



Heliophiles : 



(3) Metarrheophytes or attached flexible forms growing in mov- 



ing water. 



(4) L^/?3;rO(io/)/z3;^^5 or encrusting forms. 



(5) Herpophytes composed of small creeping algae. 



(6) Tranophytes or boring species. 



(7) Cumatophytes or *surf-loving' species. 



(8) ChordophyteSy where the thallus has the form of a cord. 



(9) Lithakophytes or lime-encrusted species (Corallinaceae). 



(10) Epiphytes. 



(11) Endophytes. 



Knight and Parke (1931) proposed a brief classification based 

 upon the same criteria, duration and perennation, Uke that Raun- 



