35 



The functions of lime salts are believed by Scliimper and others to 

 consist in merely etfcctini;- certain processes of metabolism. Schimper' 

 found that in the absence of lime the acid potassium oxalate accumu- 

 lates in the leaves and buds and acts as a poison, hence calcium salts 

 are useful, inasmuch as tliey precipitate the oxalic acid and thus pre- 

 vent its noxious action . l\ Groom ^ suggested that the injurious action 

 of the acid potassium oxalate consists in retarding the action of diastase 

 on starch, and thus its presence in the assimilating tissue brings about 

 an accumulation of starcli, due to the arrest of its transformation into 

 sugar; then, as the soluble oxalate accumulates, there is also a retarda- 

 tion in the formation of starch, and this finally leads to the death of the 

 protoplasm. Groom's theory, however, does not explain why calcium 

 is required by plants also that do not form oxalic acid, hence the bad 

 eifects caused by a deficiency of lime must be explained in some other 

 way. Although Eqitisetucea' and most ferns and grasses, and even some 

 species of the Solanacecv and LiUacew are free from calcium oxalate, 

 they all nevertheless require lime. 



Neither Schimper nor Groom have raised the question as to why 

 oxalates, even if neutral, exert a poisonous action on chlorophyll-bear- 

 ing plants, while to the writer this (juestion appeared to be the most 

 important in this connection. 



The greater lime content of the green parts tiist led the writer to 

 suppose that the chlorophyll bodies might contain calcium compounds, 

 and on the basis of this hypothesis he inaugurated a series of investi- 

 gations. Among other things, these showed that the neutral oxalates 

 are not poisonous to the lower tungi and that the development of these 

 is not at all retarded by adding considerable quantities of neutral 

 potassium oxalate to the culture solutions. Beer yeast is not injured 

 by adding even as much as 4 per cent of this salt to a fermenting 

 mixture. As in such cases the lime would become insoluble and its 

 assimilation would thus be frustrated, the writer has come to the con- 

 clusion that these organisms do not require lime.^ This is different in 

 the case of the higher alg«, however. As the chlorophyll bodies of 

 Spirogyra possess a highly differentiated structure, and even slight evil 

 effects readily manifest themselves in certain changes along their mar- 

 gin, in the retraction of the lobes, etc., vacuolation of the chloroplasts, 

 this alga was selected for the test. When Spiroyyra majuscula was put 

 into a 2 per cent solution of neutral potassium oxalate, a very striking 

 fact was brought out, many of the chlorophyll bands being injured in 

 even as short a time as thirty to forty minutes, while in even less time the 

 nucleus showed a remarkable contraction, dwindling to a mere thread 

 and thus causing a constriction of the cytoplasm where the plasma 



1 Flora, 1890, p. 209. 

 2Bot, Centralbl., 1896, No. 33. 



"Erroneous representations in regard to this point have been refuted by the writer 

 in Bot. Centralbl., 1898, Vol. LXXIV. 



