Mr. Knight on the Origin and Formation of Roots. 175 
which has dilated instead of extending itself, except that it be- 
comes capable of retaining life during a longer period ; and 
when I have laboured through a whole summer to counteract 
the natural habits of the plant ; a profusion of blossoms has 
in many instances sprung from the buds of a tuber. 
The runners also, which, according to the natural habit of 
the plant, give existence to the tubers beneath the soil, are 
very similar in organization to the stem of the plant, and 
readily emit leaves and become converted into perfect stems, 
in a few days, if the current of ascending sap be diverted into 
them ; and the mode in which the tuber is formed above, and 
beneath the soil, is precisely the same. And when the sap, 
which has been deposited at rest during the autumn and win- 
ter, is again called into action to feed the buds, which elongate 
into parts of the stems of the future plants in the spring, 
fibrous roots are emitted from the bases of these stems, whilst 
buds are generated at the opposite extremities, as in the cases 
I have mentioned respecting trees. 
Many naturalists* have supposed the fibrous roots of all 
plants to be of annual duration only ; and those of bulbous 
and tuberous rooted plants certainly are so : as in these nature 
has provided a distinct reservoir for the sap which is to form 
the first leaves and fibrous roots of the succeeding season ; 
but the organization of trees is very different, and the albur- 
num and bark of the roots and stems of these are the reser- 
voirs of their sap during the winter.^ When, however, the 
fibrous roots of trees are crowded together in a garden-pot, 
they are often found lifeless in the succeeding spring ; but I 
* M. Mirbel’s Traite d' Anatomic, &c. &c. Dr. Smith’s Introduction to Botany. 
f Phil. Trans, for 1805. 
