BOTANICAL SUBJECTS. 173 



Although these two functions of the root appertain to one and 

 the same organ, they must be kept mentally separate, in order to 

 comprehend the evolution of the root. 



There are many seaweeds which float about, like many animals, 

 without any organ of attachment. Their cells are fed directly by 

 contact with the feeding medium. They are surrounded, and 

 constantly bathed by it. It is ob\dous that when the floating 

 plant came into a region which contained plenty of nutrient 

 material, it would be to its advantage to become fixed there, so 

 that it might not be carried away into barren water by the 

 movements of the ocean. 



At first, the evolution of a root, which, after all, is only a 

 modified bud, may have had no other use than that of fixing the 

 abode of the plant on stones and rocks. The only conceivable 

 advantage of this fixation Avould appear to be that there the 

 nourishment might be more suitable and plentiful, and that the 

 plant might be in shallow water and out of the way of marine 

 herbivora. In other words, the advantages of anchorage-buds (or 

 primitive roots) would be in preventing that particular modifica- 

 tion from being washed away by ebbing tides and ocean currents. 



Oceans and seas are fed by rivers, which bring down various 

 ingredients, so that being anchored in the vicinity of the mouth of 

 a river might mean living in the midst of a rich pasturage. And 

 it seems very probable that in simple seaweeds the root had the 

 sole function of anchorage, first as a simple disk, and then as a 

 fingered or fringed disk. In those seaweeds which have more 

 complicated roots it is likely that the function of suction is added, 

 Iwth of mineral ingredients contained in the ooze and also of 

 organic matter furnished by dead seaweeds.* 



As the struggle for life forced new generations to creep up into 

 swampy ground, and then into dry land — floods and tides combining 

 to disseminate germs — the root began more and more to be of 

 essential service to the plant, the land plant being largely dejDen- 

 dent on the soil for its nourishment. As the aerial portion of the 

 plant developed, the underground portion kept pace with it, 

 becoming also woody to resist destruction by hurricanes. It is 



* Ch. Darwin relates that among the roots of Macrocystes Pyrifera are 

 entangled innumerable marine animals. These may have there some 

 unsuspected function. 



