22 CHEMISTRY OF PLANTS. 



uncrystallisable sugar. According to the researches of Mulder and 

 Crookewitt (Liebig's Ann. Bd. 44. S. 184.), inulin from the dahlia, 

 helenium, and the dandelion, in a pure state, consists of C 12 H 10 O 10. 

 It is thus isomeric with sugar and starch. Inulin has been found in 

 many places where formerly starch was supposed to be present, as in 

 tubers and fleshy roots (ex. gr. Inula Helenium, Dahlia variabilis), 

 and is probably a very widely extended substance. 



8. Fixed Oils and Wax. The great peculiarities of these physically 

 and chemically varying substances is the property of leaving upon paper 

 a transparent spot, and not adhering to water. Their colour is very 

 various ; clear, yellow, and brown. 



A. Fats (Fixed Oils). They are very widely distributed, and fre- 

 quently take the place of starch, as in the cotyledons of the CrucifercB 

 (ex. gr. the species of Brassicd], of the Synantherece (as Ilelianthus 

 annuus, Madia sativa) and many other plants. They are found in the 

 juices of the fruits and roots ; and there is, perhaps, no plant, or no part 

 of a plant, that does not contain a small quantity. The most common 

 fats in the vegetable kingdom are elain and margarin, which are formed, 

 according to Mulder, of glycerin (C 3 H 2 O), and elaic acid (C 44 H 40 

 O 4 + HO), and margaric acid (C 34 H 34 O 3 4- HO). Elain 

 is fluid, margarin solid ; and the two, mixed in various proportions, 

 form the fixed oils found in plants. Besides these, there are peculiar oils, 

 such as the cocos and muscat butters, palm and bay-berry oils. They 

 form soaps with the alkalies, which are soluble in water. Alone they are 

 insoluble in water, in ether and alcohol gradually soluble, and in volatile 

 oils perfectly so. Of their changes into the other bodies mentioned, we 

 know nothing ; at the same time it cannot be doubted, from what we 

 know of the phenomena of germination in oily seeds. 



B. Wax. This substance, which is distinguished from the oils and 

 fats through its perfect insolubility in cold alcohol, and its brittleness, is 

 found extensively in the vegetable kingdom, and plays an important 

 part. There are few plants that do not present traces of it upon their 

 surface. In all those plants and parts of plants called hoary, the delicate 

 bluish bloom consists of a thin layer of very small wax granules. This 

 layer is much thicker in the fruits of the order Myricece, of Croton sebi- 

 ferum, Tomex sebifcra, Rhus succedaneum, the leaves ofEncephalartos, the 



bracts of Musa paradisiaca and Strelitzia farinosa, the stem of Ceroxy- 

 lon andicola. In plants generally it appears to be the basis of the 

 chlorophyll ; and in many families, as, for instance, the Balanaphored* t 

 it forms the entire contents of the cells. It is found in large quantities 

 in the milky juice of the Galactodendron utile, forming the Galactin of 

 Solly. In wax two proximate principles appear to be present, myricin 

 (C 20 H20 O), insoluble in boiling alcohol, and cerin (C 10 H 10 O), 

 soluble in boiling alcohol. AVax is decidedly formed by bees out of 

 sugar. A form of wax exists, according to Avequin (Ann. de Ch. et de 

 Phys. Oct. 1840, p. 218.), in the sugar-cane, which sometimes passes into 

 sugar, and which is sometimes formed out of sugar. The wax, which is 

 combined with chlorophyll, appears to be formed from starch, perhaps 

 from inulin (see Mulder, Physiol. Chem. Moleschott, p. 253.). The 

 composition of the last form of wax, obtained from apple-peel, accord- 

 ing to Mulder, is C 40 H 32 O 10, but in most green leaves C 15 H 15 O. 

 In every case it was found poor in oxygen. The majority, however, 



* See Goppert on the structure of the Balanaphorca, in Act. Acad. Leopold. Carol. 

 Nat. Cur., vol. xviii. Supplem. pp. 236. 253. 



