Elsewhere (Provasoli, 1956) we have enumerated 

 some of the nutritional hints derivable from the 

 phyletic tendencies of algae so well described by 

 Fritsch (1934) . The Chlorophyceae and the Dia- 

 toms have strong vegetal tendencies; most of them 

 can be expected to be phototrophic . Heterotrophy 

 of the osmotrophic type is to be expected in genera 

 which contain colorless species. The Chrysophy- 

 ceae have a strong rhizopodial tendency even 

 among the pigmented species and the Eugleninae 

 and Dinophyceae have a strong tendency toward 

 loss of pigments; many species can be expected to 

 be heterotrophic or even phagotrophic . Two ex- 

 amples of the nutritional versatility of pigmented 

 algae are Ochromonas and Euglena . Ochromonas 

 malhamensis (Hutner et aL- / 1953; Aaronson and 

 Baker, 1959) , though pigmented and able under op- 

 portune conditions (high CO2) to live photoauto- 

 trophically, is preferentially an heterotroph . In 

 rich organic media, Ochromonas through many di- 

 visions, and until the organic nutrients are re- 

 duced to a low level, synthesizes only subopti- 

 mally its photosynthetic pigments: the cultures 

 appear white and the large chloroplast is reduced 

 to an anterior faint brown spot. However, when 

 the organic solutes are low and nutrient particles 

 (bacteria) are offered , it becomes a phagotroph 

 (Aaronson and Baker, 1959) . While Ochromonas 

 can utilize three methods of nutrition the Euglena 

 gracilis group is less versatile, but its photoauto- 

 trophy is as efficient as its osmotrophic hetero- 

 trophy. Therefore deductions based solely on the 



presence of photosynthetic pigments and type of 

 environment may be misleading. Species living in, 

 or restricted to polluted waters, may colonize 

 these waters for entirely different needs and are 

 not necessarily heterotrophs: Vol vox grows there 

 because it needs soluble iron and vitamins, while 

 Ochromonas prefers heterotrophy and Euglena , be- 

 sides its heterotrophic abilities , needs and toler- 

 ates NH4 in alkaline waters . 



c) Many algae require vitamins; a detailed 

 tabulation is given in a recent review (Provasoli, 

 1958) . No correlation has been detected between 

 need in vitamins and source of energy employed or 

 any particular environment; photosynthetic or color- 

 less species, species living in oligotrophic or 

 polysaprobic environments may need or not need 

 vitamins . However, the incidence of auxotrophic 

 species differs in various algae groups. (Table I) . 

 The Chlorophyceae and Bacillariophyceae have the 

 lowest number of species requiring vitamins. The 

 great majority of the Dinophyceae and Chrysophy- 

 ceae needs vitamins and all the species so far 

 studied of the Eugleninae and Gryptophyceae re- 

 quire vitamins. The need for vitamins seemingly 

 predominates in algal groups having strong animal 

 tendencies; most species of the algal groups having 

 strong vegetal tendencies (Chlorophyceae, Bacil- 

 lariophyceae, and probably Cyanophyceae) do not 

 need vitamins. Although the sampling is very 

 small, the data should be valid because the re- 

 cently studied species (all except the Chlorophy- 

 ceae) were not preselected by the choice of 



Table 1 . Vitamin requirements of algae 



Algal group 



Number 

 of 



No 



Require 



Species Vitamins Vitamins Q12 



Chlorophyceae 40 25 



Eugleninae 9 



Cryptophyceae 9 



Dinophyceae 18 2 



Chrysophyceae 13 1 



Bacillariophyceae 37 20 



Totals 124 46 



Thia- 



B12 + 



Thia- 



mine Biotin mine 



Biotin 



+ 

 Thia- 

 mine 



B12 + 

 Biotin + 

 Thiamine 



1 

 6 

 5 

 1 

 5 

 4- 

 22 



Total requirement 

 for single Vitamins 



61 



44 



86 



