34 HISTORY OF BOTANY 



barque, sc. in the inner margin adjacent to the wood, and 

 in the spring, in or through the wood itself, and there only." 



Buds arise, he thinks, by an internal pressure exerted 

 upon the wood by the turgid pith, the wood in turn push- 

 ing out the cortex and skin. He recognises the import- 

 ance of the axillary origin of buds and the economy of space 

 attained by the various methods of prefoliation, and makes 

 the very astute remark that " a bulb is, as it were, a great 

 bud under-ground." He is obviously puzzled to account 

 for the endogenous origin of secondary roots, but he notes 

 the difference in their mode of origin from that of buds. 



The leaf has none of the fundamental functions that 

 we are accustomed to ascribe to it, save that he recognises 

 that water pumped up to it from the stem evaporates 

 from its surface. Its principal use is the protection not 

 only of its younger neighbours but also of the flowers and 

 fruit, an idea he adopted from Caesalpino. Other duties 

 of leaves are to remove the " grosser parts " or impurities 

 of the sap and to act as reservoirs of superfluous materials. 

 He appears to have identified the chloroplasts, for he 

 talks of the air acting on " the acid and sulphurous parts 

 of plants for the production of their verdure ; that is, 

 they strike all together into a green precipitate." It is 

 air therefore and not light that induces greening, and this 

 error is probably due to his idea that since alkalies can 

 turn some plant extracts green, so some alkalies in the air 

 can precipitate chloroplasts in the leaf. Grew has to his 

 credit the first successful attempt to extract the green 

 pigment from leaves, using oil as a solvent, and he further 

 noticed that the solution was fluorescent. He also looked 

 on stomata (illustrations of which he gives from the pine 

 and the lily) as organs of transpiration, but he apparently 

 thought that air was admitted by them also. " But as 

 the skins of animals," he writes, " especially in some parts, 

 are made with certain open pores or orifices, either for the 

 reception, or the elimination of something for the benefit 

 of the body ; so likewise the skins of at least many plants 



