190 APPLICATIOIT OF PRINCIPLES. 



name of embryo buds ; concretions found in the bark 

 of many, and probably of all, irees, and supposed to 

 have been adventitious buds developed in the bark, 

 and, by the pressure of the surrounding parts, forced 

 into those tortuous woody masses in the shape of 

 which we find them. They, in general, present an 

 oblong or conical form, are sometimes collected into 

 clusters, and \isually exhibit little or no appearance 

 of a tendency to further growth. It is, however, 

 not uncommon to find them lengthening into branches 

 as is shown in a Poplar, for which I am indebted to 

 Sir Oswald Mosley ; and although they have never 

 yet been used for the purposes of propagation, except 

 in the case of the Olive, there seems to be no reason 

 why they should not be so employed, if any neces- 

 sity were to arise for them. The real amount of 

 their powers of growth is unknown, and would be a 

 good subject of investigation. 



CHAPTER IX. 



OF PROPAGATION BY LEAVES. 



In the beginning of the last century, Richard 

 Bradley, a Fellow of the Royal Society, published a 

 translation from the Dutch of Agricola, of a book 

 upon the propagation of plants by leaves ; in which 

 it was asserted that, by the aid of a mastic invented 

 by the author, the leaves of any plant, dipped at the 



