Bailey.] iU4 [May 1 



sive ascent is afforded by the evolution of the root as a feeding organ ; 

 and a like example of development as a result of strain is aflbrded bj^ the 

 evolution of the stem and vascular or fibrous system. Our present flora, 

 like our present fauna, is an evolution from aquatic life. The first ses- 

 sile or stationary plants were undoubtedly stemless. As the waters in- 

 creased in depth and plants were driven farther and farther from their 

 starting points by the struggle for place and the disseminating influence 

 of winds and waves, the plant body became more and more elongated. 

 Whilst the plant undoubtedly still absorbed food throughout its entire 

 periphery, it nevertheless began to difl"erentiate into organs. The area 

 chiefly concerned in food-gathering became broadened into a thallus, a con- 

 stricted or stem-like portion tended to develop below, and the entire 

 structure anchored itself to the rock by a hold-fast or grapple. This hold- 

 fast or so-called root of most of our present sea-weeds is chiefly a means 

 of holding the plant in place, and it probably absorbs very little food. 

 As plants emerged into amphibian life, however, the foliar portion was 

 less and less thrown into contact with food, and there was more and more 

 demand upon the grapple which was anchored in the soil. The foliage 

 gradually developed into organs for absorbing gases and the root was 

 forced to absorb the liquids which the i^lant needed. I do not mean to 

 say that there is any genetic connection between the sea-weeds and the 

 higher plants, or that the roots of the two are homologous ; but to simply 

 state the fact that, in point of time, the hold-fast root developed before 

 the feeding root did, and that this change was plainly one of adaptation. 

 Specialized forms of flowering plants, which inhabit water, still show a 

 root system which is little more than an anchor, and the foliage actively 

 absorbs water. The same environmental circumstances are thus seen to 

 have developed organs of similar physiological character in widely remote 

 times and in diverse lines of the plant evolution. "As the soil slowly 

 became thicker and thicker," writes King in his book upon The Soil, "as 

 its water-holding power increased, as the soluble plant food became more 

 abundant, and as the winds and the rains covered at times with soil por- 

 tions of the purely superficial and aerial early plants, the days of sunshine 

 between passing showers, and the weeks of drought intervening between 

 periods of rain, became the occasions for utilizing the moisture which the 

 soil had held back from the sea. These conditions, coupled with the uni- 

 versal tendency of life to make the most of its surroundings, appear to 

 have induced the evolution of absorbing elongations, which, by slow de- 

 grees and centuries of repetition, came to be the true roots of plants as 

 we now know them." Some aquatic flowering plants are, as we have 

 seen, still practically rootless and they absorb the greater part of their 

 food directly by the foliar parts ; but the larger number of the higher 

 plants absorb their mineral food by means of what has come to be a sub- 

 terranean feeding organ, and the foliar jiarts have developed into gas- 

 absorbing organs and they take in water only when forced to do so under 

 stress of circumstances. 



