48 



Principles: of Plant Culture. 



soil, some of which are used by the plant m growth. 

 As these useful matters are removed from the water of 

 the cells, to be formed into food (58), the supply is 

 replenished from the soil, not through any power of 

 selection possessed by the plant, but in accordance with 

 the law of diffusion. In like manner, the food formed 

 by the chlorophyll (58) finds its way to the growing 

 parts. Soluble matters not used by the plant are not 

 taken in to the same extent as those that are needed, 

 because their distribution is less disturbed. 



The distribution of soluble matter in the plant is also 

 promoted by transpiration (74). 



Section IV. The Inner Structure of the Plantlet. 



Thus far, we have consid- 

 ered the plantlet mainly 

 from the outside. Before go- 

 ing farther, it is well to learn 

 also something of its inner 

 structure. W!e have seen that 

 all parts of the plant are 

 made up of cells (12) and 

 that these cells differ in form 

 and office in the different 

 parts. The cells of the leaf, 

 for example, are different in 

 shape and in the use they 

 serve to the plant, from those 

 of the stem, flower or fruit, 

 i-der-mis) . The plant is cov- 

 skin that extends over the 



Pig. 17. Showing section 

 through leaf of Oldenburgh 

 apple. Ep. epidermis ; Pal. 

 palisade cells ; I intercellular 

 spaces. Highly magnified. See 

 also Figs. 13 and 20. 



64. The Epidermis (ep'- 

 ered by thin, translucent 



