OCCURRENCE OF CALCIUM OXALATE IN EUCALYPTUS BARKS. 27 



Text-book of Botany, p. 700, the following appears : — "The 

 importance of calcium must, therefore, be sought partly in 

 its serving as a vehicle for sulphuric and phosphoric acid 

 in the absorption of food material, and partly in its fixing 

 the oxalic acid which is poisonous to the plant, and renders 

 it harmless." Dr. Sorauer says much the same in his 

 Physiology of Plants, Weiss' translation, page 33. 



Dr. W. Pfeffer (Physiology of Plants, Ewart's translation 

 page 489) says, " as regards oxalic acid, its affinities, 

 poisonous character, feeble heat of combustion, and the 

 insolubility of its calcium salt are all points to be taken 

 into consideration." 



Such generally accepted conclusions must throw doubt 

 upon the possibility of any particular species of Eucalyptus, 

 or in fact of any other genus, to continue to form and 

 dispose of such a large amount of oxalic acid without 

 eventually suffering degeneration both in size and in robust- 

 ness. In the bark of Eucalyptus gracilis, for instance, no 

 less than 16*66°/° of the entire dried bark consisted of the 

 particular form of calcium oxalate occurring in Eucalyptus 

 barks, and some other species have been found to contain 

 almost as much. If the theory advanced is a feasible one, 

 and obtains support by further evidence, then E. gracilis 

 is also the degenerate form of a larger tree. Perhaps this 

 effect is due to the formation of oxalic acid at too rapid a 

 rate to enable the tree to continue to use it without any 

 ill effect, and other conditions be favourable, in the case of 

 certain species, the result becomes apparent in the depo- 

 sition of an increased amount of calcium oxalate in their 

 barks, which eventually brings about this stunted form of 

 growth. 



It may be thought that the shedding of the bark by 

 certain species of Eucalyptus is an effort to throw off this 

 accumulation of calcium oxalate, but the investigation of 



