THE VEGETABLE CELL 99 



Ga^^zeri saw this in Clover ; Trincliinetti saw a root of Xepefa 

 CuMria grow throiigli tlie midst of a peacli-stone, and the roots 

 of VisGum penetrate into the periderm and bark of a tree. 

 There can be no donbt, that these effects are produced by a sub- 

 stance excreted from the roots. Of what kind this is, we know 

 not; yetBecquerel (Guillemin, ^^Archiv. deBotanique,'' 1 398) has 

 given an indication in this direction, since he found that roots ex- 

 creted a free acid (probably acetic acid), or a substance which was 

 converted into an acid in air. This circumstance reminds us that 

 Lichens which live upon limestone dissolve the latter, and form 

 their fruit in excavations of it, which can only be through secre- 

 tion of a free acid. Whether the above-mentioned effects are to 

 be ascribed to the free acid excreted by roots, or to the secretion 

 of other compounds is not made out. According to BecquereFs 

 researches, this excretion of a free acid occurs not only from the 

 roots, but from the other parts of plants — ^the bulbs, tubers, buds, 

 and leaves. Becquerel brings it into connection with the evapo- 

 ration of acetic acid in human perspiration ; if this analogy were 

 recognized and the secretion thus interpreted as a true excretion, 

 there would still be no inconsistency in imagining it to exercise a 

 function, contributing towards the accomphshment of the pur- 

 poses of the living plant, even in its excreted condition. 



Ohserv. Moldenbawer (" JBeitrage z. Anatomic d, Pflanzen^' 320) ex- 

 pressed the opinioiL that the organic stibstances used by plants for their 

 nutrition, underwent a chemical decompositioii by a iiuid secreted from 

 the roots, and wei'e thus prepared for assimilation. This theory has 

 been revived, in recent tunes, by Schultz (" I)iQ Entdeckung d&r ivahren 

 PJfanzennaJiTuyig''). He believes that he found living plauts (roots a"=t 

 well as leaves) decompose solutions of the most varied organic substances 

 with evolution of oxygen, before they absorbed them; thus humous- 

 extract becomes acid, milk-sap decomposed, and cane-sugar converted 

 into starch-gum. From this he concluded that plants act on the assimi- 

 lated compounds m. a manner analogous to that of the uxtcstinal canal of 

 animals upon their food. How much of truth or error there exists on 

 this matter must be decided by future researches of chemists. 



"While some discover a removal of excrements in the secretion 

 of a watery fluid by the roots, others ascribe the same purpose to 

 an aqueous secretion through the leaves. Isolated observations 

 had long ago indicated that water is excreted, during the night 

 and morning, in the form of drops of liquid, if not from all, yet 

 from a great many leaves, since the drops of water which are 

 formed at the points and serrations of leaves, owe their origin to a 

 secretion, and not to the dew. This subject was especially fol- 

 lowed out by Trinchinetti (" On a hitherto imdescribed fit notion 

 of the Plant" — Literal hlait ^urLinncea, xi 66) ; he found little 

 glands (which he called glaiodulm periphyllce) at the spots where 

 the excretion took place ; the fluid secreted from these, though it 



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