298 ELEMENTARY STUDIES IN BOTANY 



what plants in general need, but also what that particular 

 kind of plant needs. It is also true that the needs of a plant 

 do not always remain the same throughout its whole develop- 

 ment. There are three distinct periods in the history of 

 most cultivated plants which must be recognized. The first 

 period includes germination, the starting of the plant, whether 

 from a seed, a tuber, or a bulb. The second period includes 

 growth, which means the development of a vigorous body. 

 The third period includes maturing, which means the ripening 

 of seeds and fruits, the proper development of flowers, etc. 

 The demands of the plant are different at these different 

 periods. In nature, plants have adjusted themselves to the 

 changes of the seasons, so that in general the conditions at 

 sowing time differ appropriately from the conditions at 

 harvest time ; and in general men leave their cultivated 

 plants in these particulars to the chances of nature. But 

 in proportion as the varying needs of these different periods 

 are appreciated, men will be able often to help the plants to 

 their best development. 



5. The soil. In addition to knowing the needs of the 

 plant, the cultivator of plants must know the possibilities of 

 the soil in reference to plants. We are coming to realize that 

 soil is a very complex thing and that we do not know very 

 much about it as yet. But men have used it so long in 

 cultivating plants that they have learned some of the neces- 

 sary things to do, although they may not be able to explain 

 why they are necessary. That soil in general is adjusted 

 for plant growth is evident because in nature it is clothed 

 with vegetation. But we have learned that we cannot leave 

 our cultivated plants to an unworked soil and get a respect- 

 able crop. We must know how to handle the soil so that 

 it may be adjusted in the best possible way to the needs of 

 plants. In order to adjust the soil we must know what it 

 contributes to plants, where it gets the materials to contribute, 

 how it presents the materials to the plant. If we know these 



