X] THE PLANT BASES 157 



Stachydrine, though a betaine, is included by most writers among 

 the alkaloids, and this classification has been followed here (see p. 161); 

 it is probably a derivative of proline (see p. 121). 



Betonicine, C7Hi..,0aN, is also, like stachydrine, found in the Bo tony 

 {Betonica officinalis). It is a derivative of oxyprolinc. 



Hypaphorine or trimethyl tryptophane, CnHigOaNo, occurs in the 

 seeds of a tree, Erythrina Hi/papJioru.s, which is grown for shade in 

 Coffee plantations. 



Trigonelline, like stachydrine, is usually classed with the alkaloids 

 (see p. 160) but it should probably be included among the betaines on 

 account both of its structure and of its wide distribution. 



Other betaines, trimethylhistidine, ergothioneine, occur in the 

 Fungi. 



Alkaloids. 



The plant alkaloids, so-called because of their basic properties, have 

 attracted considerable attention on account both of their medicinal 

 properties and, in many cases, their intensely poisonous character. They 

 were also the plant bases to be first investigated. As previously men- 

 tioned they are not widely distributed, some being, as far as is known, 

 restricted to one genus, or even species. Moreover, several closely 

 related alkaloids are frequently foifnd in the same plant. The orders in 

 which they largely occur are the Apocynaceae, Leguminosae, Papa- 

 veraceae, Ranunculaceae, Rubiaceae and Solanaceae. 



The alkaloids may be present in solution in the cell-sap in the 

 young tissues, but in older and dead tissues they may occur in the solid 

 state ; they may be found throughout the plant or more abundantly in 

 the seed, fruit, root or bark (quinine). 



The alkaloids are, as a rule, insoluble in water, but soluble in such 

 reagents as alcohol, ether, chloroform, etc. The majority are crystalline 

 solids which are not volatile without decomposition, but a few, for 

 example coniine, nicotine, which contain no oxygen, are volatile liquids. 



The alkaloids occur in the plant as a rule as salts of various organic 

 acids, such as malic, citric, succinic and oxalic, and sometimes with an 

 acid peculiar to the alkaloid with which it is united (e.g. quinic acid in 

 quinine and meconic acid in opium). Artificial salts, i.e. sulphates, 

 chlorides and nitrates, are easily prepared and are readily soluble in 

 water, and from these solutions the free base is precipitated again on 

 addition of alkali. 



