45 



he further asserts that only such plants can resist as have at the same 

 time a great amount of potash and phosphoric acid.^ 



Both Molisch^ and the writer'^ have observed that lime is not required 

 by the lowe rforms of algse. Molisch proved this in the case of Ulothrix, 

 Microth amnion, Stichococcus, and Protococcus,^ 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 Spirogyra, 

 where the uniting plasma bodies remain protected by the cellulose 

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

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

 forms by isogamy, but only two genera {Volvox and Eiidorina^) by 

 oogamy. In the order of the Confer voidew, Ulothrix multiplies only by 

 isogamy, while (Edogonhim multiplies by oogamy also. In other groups 

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

 Characew from the highly differentiated structure. Since neutral 

 potassium oxalate has a poisonous effect upon Diatoms, (Edogonium, 

 Cladophoray and apparently also on Braparnaldia, the presence of 

 important lime compounds in these organisms may be inferred. All 

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

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



A careful study and comparison of the various chloroplasts of algae 

 might also show certain advantages in favor of those which require 

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

 ^\>stoc 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 dili'erentiation of the chloroplasts. The beautiful chlo- 

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

 noids, which 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 the decrease of power of resistance under the 

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

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

 the yjarasites to enter. 



^Sitznngsber. d. Wiener. Akad. d, Wis8enschaften,1895, Vol. CIV. In this article 

 Molisch has also proved that the alg.e mentioned are incapable of assimilating free 

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

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



"Botan. Centralbl., 1895, No. 52. Probably A^os/ocacew and Oscillatoriaceo' also do 

 notrefjuire lime. The culture of Oscillaria, however, presents especial difficulties. 



•"It was not ascertained whether any other mode of multiplication than that by 

 bipartition would be possible in the absence of lime in some of the Ibrms 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. 



