PHANEROGAMIA : BUD ORGANS. 289 



in number, and surrounded at the base by a membranous sheath, imme- 

 diately from the branch on which the primary bud was developed. Pinus 

 and Abies exhibit the further peculiarity that they develope two, three, 

 or more primary axillary buds to true branch buds only at lengthened 

 intervals ; otherwise, in Abies, the axillary buds only exist potentially. 

 In Pinus, as has been remarked, the leaves never form the end imme- 

 diately continuing the axis, but between them is always found a very 

 small rudimentary terminal bud, which is often merely indicated by a 

 little flattened papilla composed of a few cells. Some botanists, and that 

 even recently, have esteemed these leaves as a part of the divided axis ; 

 a view which does not involve an impossibility, since in the Rhizo- 

 carpece a ramification of the axis occurs without antecedent formation of 

 buds, but which, in the way it was put forward, was a mere fancy, in 

 which the question was not once examined by a thorough investigation 

 of the fully developed parts, much less by a study of the course of 

 development. 



b. Adventitious buds of perennial plants, with vegetation periodi- 

 cally dormant. They are only distinguished from the foregoing 

 by the mode of development. Each stem, whether a common one 

 or a root stem, can develop a bud. These buds are caused, not 

 only by accidental and intentional wounding of the stem, but 

 also by the inclination of plants to develop buds at certain places. 

 Many plants exhibit upon their bark peculiar little groups of 

 lax, roundish cells, which originally lie under the epidermis, 

 which, however, is soon destroyed above them, leaving them bare 

 (lenticellce). The result of this exposure is, that at these places 

 the bark is rent by the distension of the bough or stem ; hence the 

 newly vegetating part of the bark comes in contact with the air. 

 It is principally at the edges of the rent bark that the adventitious 

 buds are found. 



Link says (1. c. 337.), the adventitious buds are distinguished from the 

 axillary buds by their structure; in the latter the greater part of the pith 

 goes with the wood into the supporting leaf, and in the former the entire 

 amount of pith passes into the bud. Accurate observation shows that 

 the supporting leaf stands in no connection with the pith, and that from 

 the wood into these only small vascular bundles enter ; whilst, on the 

 contrary, a thick cylinder of pith, and at a later period, a complete 

 circle of vascular bundles, subsequently forming wood, enter into the 

 axillary buds ; and that further, the adventitious buds stand in no 

 immediate connection with the pith, but only with the medullary rays ; 

 of this every twig of the Lime will afford an example. 



Respecting the import of the adventitious buds, I shall have to speak 

 again more fully when I come to the subject of reproduction. Here we 

 have merely to state in general terms the cause of their origination. It 

 is well known that injuries, such as the breaking or cutting off of a 

 branch, usually call forth a number of adventitious buds. Very little, 

 indeed, is yet known of the import of the lenticels in relation to this 

 point. That these are not, as De Candolle* supposed, root-buds, Du 

 Petit Thouars and H. Mohl (Flora, 1832, No. 5.) have proved beyond 

 all question, and as every attentive observer is aware. I believe that I 

 have obtained a pretty sure conclusion as to the import of these (perhaps a 



* Organographie, v. i. p. 95. 

 U 



