CHAPTER XIII 



THE WAYS IN WHICH PLANTS INCREASE IN SIZE AND 

 FORM THEIR VARIOUS PARTS 



Growth; physiological 



F all the physiological processes of plants, the one that 

 possesses the greatest interest for most people is 

 Growth. It is really a remarkable phenomenon, no 

 matter how one views it, whether in the unfolding 

 and perfecting of some favorite flower, foliage, or fruit: in the 

 development of a single microscopical egg-cell through embryo 

 seedling and sapling to a mammoth tree : or in the seasonal proces- 

 sion of vegetation from the dormance of winter through the un- 

 folding of spring, the maturity of summer, and the fruition of 

 autumn. I take it the reader does not share in the mischievous 

 fallacy that to know the causes of things is to lessen one's enjoy- 

 ment of them, and I shall try to describe the way in which these 

 various results come about. 



At first sight the phenomena of growth seem too heterogeneous 

 for analysis, but, like many another complication, they separate 

 out in their true proportions under persistent investigation. And 

 the first far-reaching fact which stands out is this, that growth 

 consists of three operations, which, often in progress together, are 

 really distinct in their nature and can proceed quite apart from 

 one another. These are, formation of new parts, or development, 

 increase in size, or enlargement, and ripening for the final func- 

 tion, or maturation. The distinction comes out very well in the 

 case of the spring vegetation. Everybody knows that the flowers 



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