Some Pure Culture Methods in the Algae

Abstract

Too much confidence has frequently been placed by algologists in their ability to recognize a given species of alga among varying numbers of other species, and in the various forms which it may assume-a fact which has led to much confusion and error, especially among members of the Protococcales. While it is now definitely known that in a number of algoe a single species may present markedly dissimilar appearances, either as a result of varying environmental conditions, or because of the presence in the life history of several unlike stages, it is certain that much of the so-called polymorphism, or pleomorphism, of algae finds its explanation in inadequate methods of study. It is becoming recognized that for life history studies in the algae it is necessary to employ cultures free from other species of algae. Even in cases where this is not, on first thought, necessary, as in the large, filamentous forms, it should be observed, for the possibility of introducing spores or sporelings of closely allied species is by no means excluded in all cases. Gratifying.progress has already been made by some algologists, working especially with members of the Volvocales and Protococcales, and it seems reasonably certain that the originally chaotic condition existing in the latter will be ultimately reduced to complete order by a careful observance of the necessity of working with pure cultures, or at least cultures containing but a single species of alga. In life-history studies where physiological differences between species are to be investigated, it is especially desirable and indeed necessary to employ pure cultures. Certain species of algae, especially representatives of the Chlorophycece, have been much used in physiological investigations-chiefly those concerning themselves with various