12 



BOTANY OF THE LIVING PLANT 



cotyledons act first as suctorial organs, and later expand into nourish- 

 ing green leaves. The root and shoot thus established may develop 

 further into a root-system and a shoot-system, as in previous cases. 



The leafy shoot of the Sunflower is produced in a manner very 

 like that of the Castor Oil. But it differs from it and also from its 

 own smooth lower parts in having a harsh roughened surface. This 

 is due to hairs of various size. The coarser types of them are seated 

 on conical outgrowths, called emergences, often of considerable size. 

 Such surface-growths, or dermal appendages as they are called, are 

 inconstant in occurrence, and irregular in distribution in plants, as 

 compared with the foliar appendages. They vary greatly in character 



in different plants, and being so incon- 

 stant, they are held as less important 

 than the axis and leaf. 



Such examples as those now given illus- 

 trate some of the differences of propor- 

 tion, and of function which may occur 

 in seedlings, while the general plan of 

 construction is the same. In each case 

 the result of germination is the establish- 

 ment of a seedling with its root-system 

 in the soil, and its shoot-system exposed 

 to the air. These regions are directly 

 continuous one with another at the level 

 of the soil. Together they form the 

 living and growing organism. They serve 

 distinct functions, but they co-operate in 

 promoting the general life of the plant. 



Each of these two regions of the plant- 

 body once established is capable of indefinite 

 extension (Fig. 5). The radicle continues 

 its apical growth, and can form an un- 

 limited number of lateral roots ; these 

 may again repeat the process. In all of 

 them also the root-tip may continue to 

 grow indefinitely. Thus a constantly 

 increasing provision is made for the 

 growing plant as regards mechanical support, and physiologically 

 for the supply of water and salts from the soil. On the other 

 hand, the stem is also gifted with continued apical growth, and 

 it has the power of forming an unlimited succession of leaves, of 



FIG. 5. 



Diagram suggesting plan of un- 

 limited growth of a Flowering Plant, 

 with multiplication of roots and 

 branches. 



