The influence of moisture upon the formation of roots by 



cuttings of ivy 



Harriet Randolph 



When pieces of the leafy stem of English ivy {Hedera Helix 

 L.) are kept for a time with one end immersed in water or in damp 

 sand, roots generally arise on the part that is submerged. If 

 the stem is then transplanted into soil, the new roots continue to 

 grow and the piece of stem becomes an independent plant. This 

 is the familiar method of raising new individuals from slips. 



These new roots may arise close to the cut end of the stem 

 and in any one or in all of the submerged internodes above the 

 cut. They are white and thickly covered with root-hairs. Their 

 structure in cross-section is shown in figure 3. When trans- 

 planted, the structure of the part subsequently formed in the soil 

 is very like that of the part that grew in water. 



The holdfast-roots, i. e. y the outgrowths along the side of the 

 stem by which the ivy clings to the wall, under ordinary circum- 

 stances remain unchanged in the water. If kept there for a long 

 time, the outer tissues decay and fall away, leaving the thicker- 

 walled central part. 



Experiments to be described below have shown that under 

 varied conditions the ivy may send out roots that differ in some 

 respects from these two kinds. 



If the slips in water are kept in a greenhouse or in a room 

 where the air is somewhat more moist than the normal, it some- 

 times happens that growth is set up in the submerged holdfast- 

 roots. Delicate white outgrowths covered with root-hairs make 

 their appearance either (i) from the tip of the holdfast-root, or (2) 

 from some point along its side, or (3) from the matted felt-like 

 complex formed by the growing together of several holdfast-roots 

 as they attached themselves to a wall. (Figure 1, lira, showing 

 near the lower end of the stem absorptive roots arising from the 

 side of the holdfast mat that had adhered to the stone.) These 

 secondary outgrowths from the holdfast -roots may occur in any 

 of the submerged internodes and without any apparent relation to 



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