OF PROPAGATION BY EYES AND KNAUBS. 185 



ly called, "eyes" (52), which are in reality rudimentary 

 branches in close connexion with the stem. All stems 

 are furnished with such buds,, which, although held 

 together by a common system, have a power of inde- 

 pendent existence under fitting circumstances ; and, 

 when called into growth, uniformly produce new 

 parts, of exactly the same nature, with respect to each 

 other, as that from which they originally sprang. 



Under ordinary circumstances, an eye remains fix- 

 ed upon the stem that generates it. There it grows, 

 sending woody 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. 29. fig. 3). This happens 

 ii\ several kinds of Lily, and in other genera. 



Man has taken advantage of this property, and has 

 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 spon- 

 taneously 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 only 

 species very generally so increased are the Potato and 

 the Yine. Of the latter, the eye, with a small portion 

 of the stem adhering to it, is commonly taken as the 

 means of obtaining young plants ; being placed in 

 earth, with a bottom heat of 75° or 80°, and kept in 



