146 Chlorophyeex 



cultures conducted by exact scientific methods have shown that specific 

 stability, even among the Protococcales, Volvocales, Flagellata, etc., is quite 

 as constant as among higher plants. 



If the cultures are carried out under conditions which are nearly 

 natural, very valuable results often accrue, but cultures in sugar solutions 

 and on gelatin or agar require the most careful interpretation. Some 

 Green Algse are much more plastic than others, but even the least sus- 

 ceptible members of the Protococcales are generally profoundly modified 

 when grown under such abnormal conditions. It is quite justifiable to 

 say that some of the statements made in consequence of the superficial 

 examination of such cultures (which often abound in monstrosities) have 

 resulted in positive harm. 



In one of his later works, Chodat ('09) has admitted that the belief in 

 wide polymorphism is not borne out by such facts as can be obtained from 

 pure cultures, and it would seem evident that his former views, although 

 based upon culture experiments, were the outcome of contaminated or 

 impure cultures. He states ('09) that there are certain Alga? which by 

 their extreme variability merit the name ' polymorphic,' if by that name 

 it is understood that a plant may present itself under many aspects without 

 change of nature ; but their polymorphism is of the same order as that 

 which is exhibited by most plants. He is also unable to support the views 

 of Hansgirg, and states that his pure cultures have shown that along- 

 side those Alga; which are polymorphic ' there are always as many, if not 

 more, which present a remarkable stability.' This is a great admission from 

 one who formerly believed in wide polymorphism 1 ; and had Chodat's pure 

 cultures been under more natural conditions, his recently expressed views on 

 polymorphism would perhaps have been even more circumscribed. 



Such polymorphism as occurs in the Chlorophycea; is of a very limited 

 character. The Protoderma-st&te of Protococcus (Pleurococcus of most 

 authors), the Dactylococcus-state of Scenedesmus] obliquus, the Palmella-state 

 of Chlamydomonas and of certain species of Ulothrix and Stichococcus, the 

 Hormidium- and Schizogonium-states of Prasiola, and the Gongrosira-st&tes 

 of Cladophora are among the few definite examples. 



SOME ECONOMIC ASPECTS OF GREEN ALG^E. The prolific growth of 

 members of the Ulvacese, more especially of Ulva Lactuca, has sometimes 

 proved a nuisance to sea-side communities owing to the obnoxious smell 



1 Another conversion, which resulted from the acquirement of greater experience, was seen 

 in the case of Klebs. The views he expressed in one of his earlier works (Ueber die For men 

 einiger Gattungen der Desmidiaceen Ostpreiissens, Konigsberg, 1879), in which he lumped 

 together all sorts of unrelated species, have received almost greater condemnation from his own 

 subsequent researches than from the work of other investigators. 



