400 ANNUAL REPORT OF THE Off. Doc. 



timothy. Among the organs of the plant, leaves and bark are rich- 

 est. Though always present in. seeds, it is much less abundant 

 than potash and than the related substance magnesia, and is one of 

 the first food materials required of the soil by the young plantlet. 



Concerning the functions of lime in the plant, much uncertainty 

 still exists. It is quite certain that all the lime present in most 

 mature plants is not of immediate utility to them, from the condi- 

 tions in which much of it is found to exist within their tissues. For 

 iu the young plant most of the lime is in a soluble condition, readily 

 expressed with the sap, and commonly in the form of the soluble salt 

 of some organic acid, such as malic acid; while in seeds much of it is 

 present in the endosferm or reserve food in combination with the 

 albuminoids, which its association renders more capable of move- 

 ment to the point of growth when germination occurs. In older 

 plants, conditions are very different; much of the lime tends to sepa- 

 rate in the form of insoluble crystals of calcium oxalate; sometimes 

 granules of calcium phosphate separate and oftimes calcium carbon- 

 ate; the last named compound is found in particular, as an examina- 

 tion of the older cell-walls. It is doubtless true that one of the 

 important uses of lime is to neutralize the oxalic acid that form in 

 considerable quantity in many plants, as the result of the oxidation 

 of their materials during the breathing process, and that would, if 

 allowed to accumulate, menace seriously the health and even the life 

 of the plants. None of the other common bases readily taken up 

 by the plant is capable of both neutralizing the oxalic acid and, 

 at the same time, removing it in an insoluble compound, from the 

 sap; for soda, potash and magnesia all form soluble neutral oxalates. 



It is true that much of the sap of plants is somewhat acid, and that 

 the growing points of most are distinctly so; nevertheless in many, 

 if not all vegetable organisms, a portion of the tissues are, on the 

 contrary, distinctly alkaline. If any great excess of feric acid is 

 from any cause accumulated, serious injury results; thus, one of the 

 observed facts concerning forced lettuce that has damped off, under 

 the influence of too elevated temperature and the increased respira- 

 tion it induces, is a marked increase of acidity. 



Schleyer (1) has made the curious observation that the und 

 chadock growing upon a soil poor in lime, blackens and dies when 

 sprayed with a 107 solution of copperas, or green vitriol, but that this 

 weed is not injured at all by even a stronger solution in cases where 

 it grows upon a soil rich in lime. The investigator suggests that in 

 the former case, an excess of free oxalic acid is present, that prevents 

 the union of the iron wilh the tannin of the plant to form a non-inju- 

 rious compound. 



If the formation of an insoluble oxalate is, however, the principal 



(1) Deutsch. eder. Presse, 29, No. 2, 12. 



