LIFE WITHOUT LIME SALTS. 53 



in soils which have been strongly limed. He believes that by this 

 means the power of resistance of these plants is diminished so much 

 that the microbes named can commence their parasitic life, and 

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

 time a great amount of potash and phosphoric acid. a 



Both Molisch & and the writer G have observed that lime is not 

 required by the lower forms of algge. Molisch proved this in the case 

 of Ulothrix, Microthamnion* Stichococcus^ and Protococcus, d and the 

 writer proved it in the case of a kind of Pahnella. 



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 

 Sjpirogijra, where the uniting plasma bodies remain protected by the 

 cellulose wall during the entire process. Some forms of the order 

 Protococcoidex multiply only by bipartition, others by swarm spores, 

 certain forms by isogamy, but only two genera ( Volvox and Eudorina e ) 

 by oogamy. In the order of the Confervoidede, Ulothrix multiplies 

 only by isogamy, while (Pdogonium multiplies by oogamy also. In 

 other groups a still higher potentialization of the nucleus has to be 

 inferred, as in the Characese from the highly differentiated structure. 

 Since neutral potassium oxalate has a poisonous effect upon Diatoms, 

 (Pdogonium, Cladophora, and apparent^ also on Dra/parnaldia, the 

 presence of important lime compounds in these organisms may be 

 inferred. All these organisms, however, are more differentiated than 

 TJlothrix, which, according to Molisch, can grow in the absence of 

 lime salts. 



A careful study and comparison of the various chloroplasts of algse 

 might also show certain advantages in favor of those which require 

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

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

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



a A satisfactory explanation of the decrease of power of resistance under the influ- 

 ence 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. 



b Sitzungsber. d. Wien. Akad. d. Wissenschaften, 1895, Vol. CIV. In this article 

 Molisch has also proved that the algas 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 Nostocacese. and Oscittatoriacese also do 

 not require lime. The culture of Oscillaria, however, presents especial difficulties. 



d 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 forms mentioned. 

 This question might also be raised in regard to fungi. 



e It would be of special interest to ascertain whether, as seems probable, Eudorina 

 and Volvox require lime salts. 



