42 PEOPAGATIOiT 0* PLAKTS. 



lished far away from the parent stock. While such plants 

 do not migrate, or move about in the same manner as the 

 floating aquatic herbs, still each successive generation 

 seeks a new abiding place, at a greater or less distance 

 from the homes of their immediate progenitors. 



Wherever a plant becomes established, the roots gather 

 nutriment from the medium in which they are placed, 

 and of such nature as is required to build up the struc- 

 ture. These nutrients are absorbed or taken in through 

 the surface of the roots, and as all must pass through 

 the minute cells, it is quite evident that they can only be 

 utilized when in a liquid or gaseous condition ; nothing 

 of a solid nature can be appropriated for use by the plant. 

 Everything found in a mature plant must have originally 

 entered the root or other parts as a liquid or gas, and 

 then changed, by some chemical or other agency, into 

 whatever form it afterward assumes. 



Whether roots possess an inherent power of selecting 

 their food, or not, is still a mooted question among veg- 

 etable physiologists. Some are quite positive that they 

 do possess this power in a greater or less degree, while 

 others are just as certain that they do not, and that all 

 matter presented to them in a liquid or gaseous form is 

 alike absorbed ; hence the frequent cause of death among 

 plants through the absorption of poisons. Dr. W. B. 

 Carpenter, in his " Vegetable Physiology and Botany," 

 in referring to this subject, says : "that they appear to 

 have a certain power of selection ; some of the substances 

 dissolved in the fluids which surround the roots being 

 absorbed and others rejected. Thus, if a grain of wheat 

 and a pea be grown in the same soil, the former will ob- 

 tain for itself all the silex or flinty matter which the 

 water of the soil can dissolve ; and it is the deposition of 

 this in the stem which gives to all the grasses so much 

 firmness. On the other hand, the pea will reject this, 



