264 PROPAGATION BY EYES. 



matter downwards over the alburnum, and a new branch 

 upwards, clothed with leaves, and perhaps flowers; but it 

 occasionally happens that eyes separate spontaneously from 

 their mother stem, and when they fall upon the ground they 

 emit roots and become new plants (p. 44, Fig. X.). This 

 happens in several kinds of LUy, and in other genera. 



Man has taken advantage of this property, and discovered 

 that the eyes of many plants, if separated artificially from the 

 stem and placed in earth, will, under favourable circumstances, 

 produce new plants, just as such eyes would have done if they 

 had spontaneously disarticulated ; hence the system of propa- 

 gation by eyes, an operation employed only to a limited extent 

 in actual practice, but which in theory seems applicable to all 

 plants whatever. The species most generally so increased are 

 the Potato and the Vine. Of the latter, the eye, with a small 

 portion of the stem adhering to it, is commonly used as 

 the means of obtaining young plants ; being placed in earth, 

 with a bottom heat of 75° or 80°, and kept in a damp atmo- 

 sphere, it speedily shoots upwards into a branch, and at the 

 same time establishes itself in the soil by the development of 

 the requisite quantity of roots. In order to insure success in 

 this operation upon the Vine, it is only necessary that the eye 

 should be dormant, and that a small piece of well-ripened wood 

 should, as has been already stated, be separated with it ; it will 

 then grow ia much the same way, and under the same circum- 

 stances as a seed. There is no doubt that many plants could 

 be thus multiplied as easily as the Vine, but it is equally certain 

 that a far larger number cannot be so increased. The reason 

 is, probably, that such eyes are not sufi&ciently excitable, and 

 that consequently they decay before their vital energies are 

 roused ; and, in addition, that they do not contain withia them- 

 selves a sufficient quantity of organisable matter upon which to 

 exist until new roots are formed, and capable of feeding the 

 nascent branch. 



Mr. Knight's explanation of this, although in part applicable 

 to cuttings only, yet seems to deserve being introduced in this 

 place. " Every leaf-bud is weU known to be capable of extend- 

 ing itself into a branch, and of becoming the stem of a future 



