DEVELOPMENT. 73 



with the great quantity of water they contain. Growth, in 

 fact, is but the preparatory stage, during which material 

 and machinery are acquired, to be turned to subsequent use 

 in the consolidation of the stem, the construction of flower 

 and seed, the formation and storage of reserve food -materials, 

 of starch, of oil, of the various secretions, such as the 

 caoutchouc, the alkaloids, as quinine, morphia, and many 

 others. 



Growth and development may go on together at the 

 same time, as we see in an oak tree, which puts forth its 

 midsummer shoots at the same time that it is ripening its 

 acorns and consolidating the new wood ; but in an herba- . 

 ceous plant, like the wheat, as development proceeds, 

 growth ceases at least, to a great extent. So in the case 

 of such plants as the turnip, the mangel, and the hop, 

 when the plant commences to enter upon the flowering 

 stage, then changes not merely of bulk, but of outward 

 form and to some extent of inward construction and che- 

 mical composition occur. So, as the soft tissues harden 

 into solid wood by deposit of woody matter in their wood 

 cells, development takes place ; and, as the water and the 

 salts taken up by the roots and the gases inspired by the 

 leaves act and re-act upon one another aided or not, as 

 the case may be, by the agency of light various changes 

 occur which may be included under the head of develop- 

 ment. Development, then, is morphological in so far as it 

 relates to the conformation of the plant, chemical or phy- 

 sical in so far as it includes the chemical and physical 

 changes which accompany the passage from the young to 

 the old, from the crude and imperfect to the complete and 

 mature. The conditions which favour development in the 

 sense here understood are thus more or less opposite to 



