42 PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



Thus far the only plants which have been proved positively to 

 develop without lime salts are lower forms of algre and fungi. 



Like Boehm, Schimper observed an abnormal accumulation of starch 

 where there was a deficiency of lime, but he declares this to be a mere 

 secondary pathological phenomenon, and pointed out that even leaves 

 which are packed with starch may die. This, however, can not be 

 regarded as a refutation of Boehm's views. In order to render starch 

 available for respiration it must be saccharified. In Schimper 1 s case a 

 failure to produce diastase might adequately account for the result. 

 Other discrepancies between the observations of several authors may 

 have their origin in the different lime content of the seeds used for 

 the experiment. 



Raumer" agrees with Boehm in ascribing to the lime the function of 

 aiding 1 in the growth and solidification of the cell walls but he does not 

 agree with his other views. However, his reason for believing that lime 

 has nothing to do with the transportation of starch is not convincing. 

 Certainly, the mere chemical process of forming starch from sugar 

 does not require lime, but the formation of leucoplasts and chloro- 

 plasts — the indispensible apparatus for starch formation — may 

 require it. 



Holzner's view 7, that lime salts aid in the assimilation of sulphuric 

 and phosphoric acids is very improbable, .since his hypothesis would 

 require the formation of <»x:ilic acid in every protein producing cell — a 

 condition which is not realized, and. moreover, the assimilation of these 

 acids also takes place in fungi in the absence of every trace of lime suits. 

 Finally, Hornberger'' and others have objected to this view as not 

 agreeing with their observations. 



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

 consist in merely effecting 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 they precipitate the oxalic acid and thus pre- 

 vent its noxious action. P. 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 starch, due to the arrest of its trans- 

 formation into sugar; then, as the soluble oxalate accumulates, there 

 is also a retardation 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 also by plants that do not form oxalic- 

 acid, hence the bad effects caused by a deficiency of lime must be 

 explained in some other way. Although Equisetacese and most ferns 



"Landw. Vers. Stat., 1881], Vol. XXIX, p. 271. '' Flora, 1890, p. 200. 



'-Flora, 1867, p. 497. 'Bot. Centralbl., 1896, No.:;.".. 



cLandw. Jahr!>., 1882, Vol. XI. p. 455. 



