100 



THE METABOLISM OF ALGAE 



The unsaponifiable lipoid fractions of all algae appear to 

 contain small amounts of the paraffin hydrocarbon hentria- 

 contane, C3iH64.^*^' ^^ Sterols, similar to those of higher 

 plants which are grouped under the generic name of sito- 

 sterol, have been found in the Chlorophyceae, Xantho- 

 phyceae and Rhodophyceae.^*^' ^^ A more well-defined 

 compound, fucosterol, occurring in representatives of most 

 algal classes but not in higher plants, is the only sterol 

 produced by the Phaeophyceae.^^ The Chlorophyceae are 

 somewhat variable in the sterols which they contain; thus 

 Oedogoniiim sp. contains only sitosterol ;^^^ Cladophora 

 saiiteri and Nitella opaca contain both sitosterol and fuco- 

 sterol;^^^ the principal sterol of Chlorella pyrenoidosa is ergo- 

 sterol, a sterol which is otherwise known only from fungi 

 and lichens;^^^ and Scenedesmus ohliquiis contains chon- 

 drillasterol amounting to about 23 per cent of the unsaponi- 

 fiable fraction, apparently to the exclusion of other sterols. ^^ 



CH3 



I 

 CgHj 3Crl2CH2^^ 



CHCH3 CH3 



II I 



(CH 3) 2CHCCH oCH 2CH 



HO\/\/ 

 j3-sitosterol 



/\y\/~ 



HOX/X/ 

 fucosterol 



C2H5 



CH, 



(CH3)2CHCH(CH3)CH:CHCH(CH3) (CH3)2CHCHCH:CHCH 



'\/\/' 



HO\/\/ 

 ergosterol 



HO\/\/ 

 chondrillasterol 



