S06TS AND THEIR FtTNCTIOiSrS. 39 



of parasites point toward the center of their host. While 

 the first root of the plantlet growing in the earth, and in 

 a position free to act, generally goes downward, the sec* 

 ondary or adventitious roots have a tendency to wander 

 in search of food, not only pushing out at right angles 

 from the central descending axis, but often climb up 

 banks at a very acute angle. There is no doubt about 

 the uniformity of action in first roots of plants, bat those 

 produced later are controlled by varying conditions and 

 circumstances. 



The sensitiveness of the root is mainly in its point, 

 and it is through the younger parts that the nutrient 

 properties are mostly absorbed from the medium in which 

 they live. Old or large roots cannot take up moisture or 

 the elements of nutrition necessary for the growth of the 

 stem and its appendages ; hence the necessity of preserv- 

 ing the small fibers from injury in transplanting, as well 

 as placing the principal roots in a position where new 

 rootlets will be produced in time to respond to a call 

 upon them for nutriment by the leaves. 



The most natural position for roots is at the base of 

 the stem, whatever form the latter may assume, whether 

 it be that of a tree, shrub, vine, herb, bulb, tuber, epi- 

 phyte, or even a parasite, which pierces with its roots the 

 tissues of its host for nutriment. But as all roots are 

 produced by the multiplication of cells within restricted 

 limits, they may, like the adventitious bud, appear, under 

 favorable conditions, upon all parts of the same plant — 

 on the stem, leaves, buds, or other appendages. Roots 

 have no more fixedness of character than branches, for 

 they may in many instances be changed into stems or 

 branches, and there are some kinds of trees, like the Wil- 

 lows and Poplars, that may be completely inverted, tliu 

 roots becoming branches and the branches roots. The 

 same is true of many other kinds of plants to which I 

 shall have occasion to refer hereafter. 



