424 The Rev. P. Kzrrn on the Origin of Buds. 
plants which have their diameters augmented by the addition 
of annual and concentric layers. It may include dicotyledonous 
perennials ; but dicotyledonous annuals, and monocotyledonous 
plants, as well as plants without cotyledons, it cannot possibly 
apply to. due : 
It is admitted that buds, though not originating as above, 
may be produced from any layer of alburnum by artificial 
means ;—what are these means ?—but it is contended that Na- 
ture never protrudes a branch-bud except in the aforesaid way. 
At all events, the discovery is not entirely new. It is at least 
as old as the researches of Mrs. Ibbetson, who saw, as I be- 
lieve, through the medium of the microscope, the buds in the 
very act of crossing the concentric layers on their way to the 
alburnum, and who has advocated and illustrated the fact and 
the doctrine with the most laudable zeal*. She thought, in- 
deed, that the bud is originally formed in the root, from whence 
it ascends by ** the line of life" —that is, the medullary sheath— 
till at last some unknown but potent and irresistible cause gives 
it a horizontal direction, and forces it ultimately to the circum- 
ference, in spite of all intervening layers of wood, however nu- 
merous and however hard. "This was indeed very difficult to 
believe ; and was, as I should suppose, never much believed. 
. But the subject was not left to be elucidated merely by the 
labours of Mrs. Ibbetson. It had long occupied the attention 
of M. Du Petit-Thouars, a French botanist distinguished for 
his able Illustrations of the Plants of Madagascar. In a paper 
entitled De la Terminaison des Plantes, and read at a sitting of 
the Royal Academy of Sciences on the 7th of October, 1816, he 
exhibits the result of his observations, and develops his views 
at some length. The following extracts will show that the 
doctrine of the central origin and horizontal protrusion of buds 
* Phil. Mag. vol. 45. 56. 
comes 
