304 



Recent cultural experiments with grain, buckwheat and Elodea cana- 

 densis'^ in nutrient solutions, free from calcium, showed that after a five day 

 retention in a solution free from calcium, the root growth became less and 

 later ceased entirely. The roots turned brown and the root cap died. Pe- 

 culiar, brownish spots were found on the leaves, which soon went to pieces. 

 The content in acid potassium oxalate and in starch was greater than ixi 

 normal plants. The death of plants, in a nutrient solution without calcium, 

 has been traced by Loew to a poisonous action of the magnesium salt. 

 Rruch's cultural experiments with magnesium sulfate, nitrate, carbonate, 

 and phosphate in aqueous solutions showed that the roots, to be sure, soon 

 stopped growing, but the aerial parts developed further perfectly normally 

 and even blossomed. W'heat plants in solutions free from calcium and 

 magnesium died far more quickly than those in solutions lacking only the 

 calcium. 



Amar'-' observed the absence of calcium oxalate crystals in those leaves 

 which were formed after the i)lants had been put in a solution free from 

 calcium. 



A further insight into the conditions due to a lack of calcium is given 

 by Kriiger and Schneidewind through Schimper's statement that, when the 

 calcium is removed, all the symptoms of poisoning from an enormously large 

 content of acid potassium oxalate are indicated. In Phaseolus these authors, 

 to be sure, could prove no especial increase of a strong organic acid. They 

 succeeded, however, in keeping the plants until all the reserve substances 

 had been used up by painting dying seedlings with a calcium solution either 

 on the hypocotyles or at the place where death usually begins. This sub- 

 stantiates Bohm's observations that seedlings of the scarlet-runner bean 

 take up calcium as well as water through the outer skin f)f the petioles and 

 leaves. 



The experiments of Moisescu'' confirm the above observations. He 

 found in different cultures in nutrient solutions that those seedlings had be- 

 came aiTected earliest and most extensively which had grown in solutions free 

 from calcium. In Platanus orientalis, the leaves of which partially became 

 brown and dry along the veins, it was found that the diseased ones contained 

 twice as much acid as the healthy ones. Gloeosporium nervisequum in- 

 fested the diseased leaves. On this account it must be assumed that the 

 parasite named attacks only weakened leaves. This weakness would con- 

 sist here of "Cakipenuria," that is to say, a lack of calcium. In the author's 

 opinion, not enough calcium was present to convert the excessive potassium 

 oxalate into calcium oxalate. 



Besides cultural experiments of this nature, a large number of practi- 

 cal results point to the injuriousness of calcium poverty. At least we find 

 in many cases a cessation of the phenomena of disease after an addition of 



1 Bruch, p., Zur physiologischen Bedeutung- des Calciums in der Pflanze. 

 I.nndwirtsch. .lahrb. 1901. Suppl. III. p. 127. 



2 Amar, Maxime, Sur le role de I'oxalate de calcium dan.s la nutrition des 

 vegetaux. Annal. sc. nat. bot. 1904. XIX, p. 195. 



3 Moisescu, N., p:in Fall von Calcipenuria. Zeitschr. f. Pflanzenkr. 1905, p. 21. 



