THE SAP OF PLANTS. 79 



drj% and the bulbs became fully ripened. In October I commenced 

 potting, &c., as before. It is very essential to get the bulbs well 

 ripened. 



A collection of Ixias, Sparaxis, Tritonias, Babianias, and all others 

 of what are termed Cape Tridaea, ought to be grown wherever there be 

 facilities for it. They form a most beautiful display, are easily grown 

 with little trouble, and may be procui-ed at a trifling expense. 



THE SAP OF PLANTS. 



BY SENEX. 



Having noticed inquiries in the Cabinet relative to the nature and 

 movements of the sap of plants, and no specific replies having been 

 given, I have extracted the following from Dr. Lindley's " Introduc- 

 tion to Botany,"* which will fully elucidate the subject, and I shall 

 be glad to observe its appearance in an early number, as it will contri- 

 bute useful hints to cultivators of plants, tiiat may be applied at the 

 early stage of spring growth. 



" Of the Sap. — For the sustenance of plants a fluid is neces- 

 sary, which is absorbed by the roots from the earth, then sent 

 upwards into the stem, afterwards impelled into the leaves, whence it 

 descends through the liber, transferring itself to the inmost parts of the 

 wood. Tills fluid, which constitutes the blood of plants, is called the 

 sap. When first introduced into the system, and even when altered in 

 some degree by having dissolved the various substances it encounters 

 in its passage, it is true sap ; afterwards, when its nature has been more 

 changed by elaboration in the leaves, it becomes what is called the 

 proper juice. 



" If the sap be examined in its most simple state, it will be found to 

 consist of water, mucilage, and sugar. As the two last can scarcely 

 have been absorbed directly from the earth, it is inferred that, as soon 

 as the fluids taken up by the roots enter the sj'stem, they suffer some 

 chemical decomposition, the result of which is the production of muci- 

 lage and sugar. In addition to the supply of sap which is obtained by 

 the roots, a certain quantity is, no doubt, also absorbed from the atmo- 

 sphere by the leaves, as is evident from succulent plants, which will 

 continue to grow and acquire weight long after their roots are severed 

 from tiie eartii. This absorption on the part of the leaves chiefly takes 

 jilace during the night, or in cloudy weatlier ; while perspiration, on the 

 otlier hand, goes on in the day-time in bright weather. 



•' With regard to the cliemical nature and changes of the sap, I 

 cannot do better than give the statement of Link, with some necessary 

 alterations. ' The food of plants must be composed of oxygen, hydro- 

 gen, carbon, and azote. Water consisting of oxygen and hydrogen 

 alone is not sufficient. Many experiments, indeed, have been instituted 

 to prove that pure water is a sufficient food, especially by Van Helmont, 

 EUer, Bonnet, Du Hamel, and others ; but it is probable, as Walerius 



* This work we recommend to the attention of all gardeners and bo'.anists. — 

 Conductor. 



