b ELEMENTS OF BOTANY. 



dowecl many plants with the power of putting forth roots as occasion may 

 require from any part of the stem, or even, in some instances, from the 

 leaves, thus giving them a double hold on life : such are denominated 

 secondary or adventitious roots. The common strawberry of our 

 gardens will serve as an illustration of one kind of adventitious roots. 

 This plant produces "runners," which put forth roots at the point where 

 they touch ground, then a cluster of leaves, and a new plant is formed. 

 The stems of the running blackberry (Rubus Canadensis L.) often root freely 

 also, and form a netting for the feet of the unwary. Very many illustra- 

 tions of plants endowed with this power might be found anywhere about 



Fig. 12. — Common ivy (Hedera Helix), with adventitious roots. 



us, but it remains for the skilful gardener to develop it to its fullest ex- 

 tent, as his cuttings of roses, geraniums, and indeed of almost all his rarest 

 and most beautiful blooming plants abundantly testify. 



Such adventitious roots are, however, true roots, which perform the 

 ordinary functions of such organs. There are other adventitious roots of 

 an entirely different character. The stem of the poison ivy (Rhus Toxicoden- 

 dron L.), when growing beside some object to which it can cling, puts 

 forth roots in innumerable numbers which do not contribute in any de- 

 gree whatever to the nourishment of the plant, but merely afford mechan- 

 ical support. Moreover, these roots appear to be produced in response to 



