45 



be fnrtlier asserts tliat only such i)liiiits can resist as have at the same 

 time a great amount of potash and phosi)hoii(' acid.' 



lioth Molisch- and the writer ' have observed th;it lime is not lequired 

 by the lowe rtbrms of n\g',i\ Molisch proved this in the case of UJolhrix^ 

 Microthamnion, Stivhococcus, and Frotococcus,^ and the writer proved it 

 in the case of a kind of Palmella. 



Bipartition, zoospores, isogamy, and oogamy represent a scale of 

 progress which probably requires an increasing differentiation of the 

 nuclei. Isogamy in its simpler forms must be distinguished from its 

 more perfected form, as it is found for instance in copulation of Spirixji/ra, 

 where the uniting plasma bodies remain protected by the cellulose 

 wall during the entire process. Some forms of the order Profococ- 

 coidcff multiply only by bipartition, others by swarm spores, certain 

 forms by isogamy, but only two genera { Volvox and Eudorina-') by 

 oogamy. In the order of the Goufervoidecr, Ulothrix multiplies only by 

 isogamy, while (Edofioninm nniltiplies by oogamy also. In other groui>s 

 a still liiger potentialization of the nucleus has to be inferred, as in the 

 Chdracav from the highly ditlerentiated structure. Since neutral 

 potassium oxalate has a i)oisonous effect upon Diatomf, G^dorfonium, 

 Clddophora, and apparently also on Bniparnnldw, the presence of 

 important lime compounds in these oiganisms may be inferred. All 

 these organisms, however, are more differentiated than Ulothrix, which, 

 according to Molisch, can grow in the absence of lime salts. 



A careful study and comparison of the various chloroplasts of algfe 

 might also show certain advantages in favor of those which reciuire 

 lime for their development. For instance, certain low genera, such as 

 Nostoc and Oscillaria, form no starch, while others do. In such cases 

 starch formation is to be regarded as a step forward, one that depends 

 upon a higher differentiation of the chloroplasts. The beautiful chlo- 

 roplasts of Spirogyra show a high degree of differentiation, the pyre- 

 uoids, wliich form stations in the chloroplasts, being the manufacturers 

 of the starch. 



It is true Schmitz also observed well-defined chloroplasts multiplying 



'A satisfactory explanation as to tlie decrease of power of resistance under the 

 intiuence of such an important nutrient as lime would be very desirable. Perhaps 

 the cells beneath the lenticels are thereby stimulated to growth and open a way for 

 the parasites to enter. 



^Sitznngsber. d. Wiener. Akad. d. Wissenschaften, 1895, Vol. CIV. In this article 

 Molisch has also proved that the algic mentioned are incapable of assimilating free 

 nitrogen. This confirms an earlier observation on Noatoc by the writer (Biol. Cen- 

 tralbl., Vol. X, p. 591) and a later observation by Kossowitsch. 



^Botan. Centralbl., 1895, No. 52. Probably ^Vosfocat'(w and OsciHa<onace«; also do 

 notrerjuire lime. The culture of Oscillaria, however, presents especial dlfficultiea. 



■lit was not ascertained whether any other mode of multiplication than that by 

 bipartition would be possible in the alisenceof lime in some of the forms mentioned. 

 This question might also be raised in regard to fungi. 



^It would be of special interest to ascertain whether Eudorina and Volvox require 

 lime salts. They probably do. 



