120 Vegetable Physiology. 



touch the water, they will absorb moisture sufficient to make 

 the plant flourish. The knowledge that the fibres arc the true 

 and only organs of absorption, has a very important practical 

 application. It often happens in transplanting trees, or other 

 plants whose roots are much branched and extend deeply into 

 the ground, that sufficient care is not taken to preserve the 

 delicate fibres and spongioles uninjured, and the consequence 

 is that the plant languishes or dies. This may be obviated bv 

 carefully digging around the roots so as to include the whole 

 and then removing the earth from among them in so gentle a 

 manner as not to break ofFor bruise their fibres. The growth 

 of roots always takes place in that direction where they can 

 find moisture, and on this account, some writers have attributed 

 to them a species of instinct. The fact can, however, be 

 explained on the principle that the soft points of the fibres will 

 naturally extend themselves most where there is least resist- 

 ance ; and moist earth is always softer than dry. The same 

 principle will account for the occurrence, which sometimes 

 takes place, when the roots of a tree insinuate themselves 

 between the stones of a wall, or ruined building. In this case 

 meeting with an obstacle to their growth, in the stones, they 

 turn into the crevices, and the fibrils grow by their own 

 absorption and the nourishment sent to them, until they become 

 so distended as to force the stones apart, and even throw down 

 the wall. Roots are ordinarily distinguished from stems, not 

 only by their direction, and by the presence of the absorbing 

 fibres, but also by the absence of buds. This last circumstance 

 is more characteristic of the root than any other, since the part 

 of the axis above ground is not always a stem, nor that under 

 the ground always a root. The two parts may sometimes 

 indeed be transformed into each other. The branch of almost 

 any tree, upon being stuck into the ground, will produce root- 

 fibres, and form a new plant, while there are some instances 

 in which a tree or shrub may be inverted, and made to grow 

 with the roots in the air. A very beautiful example of the 

 structure of the fibre and spongiole, may be observed in the 

 little Duckweed, (Lemna minor,) which is found floating like a 

 green scale, in every piece of stagnant water. From the cen- 

 tre of each leaf hangs down a single fibre into the water, with 



