2h ee aa sel ee “8 aoe ya 2g) a oa dies : 
eee -NoTES ON SCIENTIFIC RESEARCH, | 105 
n alcohol 95 per cent., insoluble in alcohol 40 per cent., soluble in ether, insoluble © 
in glacial acetic acid +15 per cent. water, but readily soluble in pure glacial acetic 
cid, coloured brown by osmic acid and black by ammoniated nitrate of silver. The 
_ secretion is lighter than water and evaporates at 120°. | 
<= Meyer tried with succes to obtain a substance of the same properties as the secre- 
_ formed during the assimilative process, by heating powdered leaves and then by 
extracting with ether. He presumes that the leaf-aldehyde, discovered by Curtius, Reinke 
and Franzen*) in the green parts of plants, and which they considered to be «,$-hexylene 
"aldehyde, is the chief component of the secretion. The general occurrence of the hexylene 
a _ aldehyde i in all the leaves examined corresponds with the general presence of the secretion 
| in the chloroplasts of the leaves. The chloroplasts of etiolated leaves do not contain 
any secretion due to assimilation. This is why no aldehyde can be obtained from etio- 
lated germs. It is to be presumed that other substances participate in building up the 
secretion, such as hexylenic acid and its homologues, the higher homologues of the 
_a,8-hexylene aldehyde and hexylene alcohol, bodies obtained by .Curtius and Franzen 
on distilling leaves with steam. 
Up to a certain degree, the presence of a hexylenic alcohol in Japanese peppermint 
oil, as observed by us, may be looked upon asa confirmation of Meyer’s results. It is 
_ true, however, that we found an alcohol of a somewhat different structure from that 
which would correspond to a «,-hexylene aldehyde, for as we stated on page 39 of 
_ this Report, it is a 8,y-hexylene alcohol. 
The importance of the emdermis for the Geunlaiive process in plants. — How and 
"where the different plant substances are formed,and for what purpose, is an unsolved 
question still in most of the cases. As far as essential oils are concerned, they are 
_ considered sometimes as a protection against excessive radiation of heat during the 
“night, against excessive evaporation in day-time, against being eaten by animals, as an 
attraction for insects; sometimes as final products of the assimilation and as useless 
_ ballast. Be it as it may, the place where they where formed was not known, only the 
‘view that no chemical process of building up or down took place in the epidermis was 
sustained by a good many. This is not the case, however, as A. Tschirch?) explains in 
a treatise on the localization of chemical work in the plant. About 40 years ago, it was 
still taught that the epidermis of plants was void of substance and if slides were made, 
_ they seemed to confirm this view. Colourless protoplasm or, in the case of red leaves, 
_ a red solution was all that could be seen. The chemical process of building up, it was 
_ Said, was only carried out by the plasma of the cells. 
Already a year ago, Tschirch has shown, that there is a certain membranous layer 
‘Tight through the whole plant, that has no direct contact with the plasma but is fit to be 
_ chemically active and that this membranous layer is either the intercellular substance 
" itself, or originates from it or is the direct continuation of it. 
- As to the epidermis, it is a well-known fact that it may contain representatives of 
_ two important classes of bodies; viz., alcaloids and glucosides. This conviction has only 
_ slowly gained ground. When Zoepilis the Mentha and Conium species for the anatomical 
atlas, which he edited together with Oesterle, Tschirch observed that the material pre- 
3 "pared with alcohol showed sphzro-crystals in the epidermis, and only there. It was easy 
_ to comprobate that such crystals were also to be found in many other plants under the 
*, 
_ ~ +4) Comp. Reports April 1911, 160; October 1912, 138. — 7”) Berichte d. deutsch. pharm. Ges. 27 (1917), 
_ Schweiz. Apotheker-Ztg. 56 (1918), 162, 173, 175. 
