83 CELLULAR TISSUE. 



after boiling with dilute hydrochloric acid, and subsequent successive treatment with 

 ammoniacal sub-oxide of copper, hydrochloric acid, potash, ether, and alcohol, to be non- 

 nitrogenous, consisting of the body which he calls cutm, and for which he gives the 

 following percentage composition— C, 73, 66 . H, 11, 37 . O, 14, 97. The cutin shows 

 the properties above described (p. 74). When heated it gives fatty acids, on treatment 

 with boiling nitric acid, suberic acid, and may be saponified by boiling with con- 

 centrated solution of potash. The cuticle and cuticular layers of the leaf of Agave 

 Americana, after their isolation by Fremy's method, appeared to me to have retained 

 their structure completely: they still retained traces of cellulose which could be 

 determined microchemically. An analysis completed once in Halle, in Professor 

 Stohmann's laboratory, showed the substance to be completely non-nitrogenous. 



Sect, 17. In company with the cuticular bodies there are usually found com- 

 pounds of a waxy nature, i. e. carbon compounds, the chemical constitution of which 

 requires, it is true, more careful investigation, and perhaps is not very closely allied 

 to that of bees-wax, but which in their physical properties as now known, such as 

 solubility, fusibility under 100°, &c., resemble the better known sorts of wax, and 

 therefore may for the present be shortly termed wax. As regards their solubility, all 

 the allied waxy bodies are soluble with difficulty or not at all in cold alcohol, but com- 

 pletely in boiling alcohol. Most of them, but not all, dissolve in ether even without 

 any considerable rise of temperature. According to the incomplete investigations 

 hitherto made, many sorts of wax found on the epidermis prove to be mixtures of 

 two or several bodies : with many there is mixed a considerable quantity of resin, 

 easily soluble in cold alcohol, e. g. with the wax of the stems of Ceroxylon, Klop- 

 stockia, and Chamsedorea ; a compound of Silicon is mixed with others (stems of 

 Chamsedorea and Kerria) ^. 



Wax is not present, according to the existing investigations, in the epidermis of 

 parts which are submerged, or underground. In epidermal layers however which 

 are surrounded with air it occurs very generally, perhaps even universally, partly 

 imbedded in the cell-wall, partly extended on the outer surface of the cuticle as 

 a wax-covering. 



Imbedded wax occurs only in those walls which consist of or contain cutin, 

 and not in the relatively pure cellulose membrane. It is found both in those which 

 simultaneously extrude wax-coverings, and also in others in which the latter are 

 absent or only very slight, such as the stems and branches of Acer striatum, Sophora 

 japonica, Jasminum fruticans, the foliage leaves of Cycas revoluta, Aloe verrucosa, 

 Epidendron ciliare, Hoya carnosa. The imbedded wax is disposed in the cuticular 

 membrane in the form of small bodies, which, in fresh preparations, cannot be 

 recognised optically. It is determined anatomically, by fusing it out of the 

 sections by carefully warming them in water. It then exudes from the cuticle 

 and cuticular layers in the form of small drops. Boiling alcohol extracts it from 

 the membranes. The latter, after the wax has been fused or dissolved out, retain 

 their original structure. But where the infiltration of wax has been excessive (Acer 

 striatum, Klopstockia) their volume is considerably reduced, the reduction remaining 

 even after subsequent treatment with water. 



' On the composition of the bodies in question, compare Wiesner, Botan. Zeitg. 1876, p. 325. 

 postscript. 



