474 On the Structure of Roots. 



overlooked. The daisy, the primrose, the flag, in fact nearly all 

 the herbaceous perennials of our gardens, with the perennial 

 grasses, sedges, rushes, &c,, are examples of plants in which 

 the main stem does not ascend above ground, but creeps along in 

 the manner of a root, beneath the surface, throwing out adventi- 

 tious roots below, and leafy flowering stems above, which sprout, 

 flourish, and disappear, in successive generations, corresponding 

 to the annual foliation of a tree, while the main trunk, called by 

 botanists a rootstock, maintains itself during a more or less extended 

 period of existence. These rootstocks are very like roots when 

 viewed superficially. They are vulgarly called roots, and it is a 

 familiar phrase in reference to propagating these plants to say we 

 part the roots. Now, no one ever raised young oaks from frag- 

 ments of the root ; as a general rule, pieces cut from the roots of 

 plants with upright stems die away and produce nothing. 1 his 

 point is also illustrated by organs which have undergone a parti- 

 cular modification which aff'ects both stems and roots. We can 

 cut a p6tatoe into a number of pieces and raise a plant from each, 

 but it is useless to cut up a carrot or a turnip with a similar 

 expectation. The latter are roots, the potatoe, although commonly 

 called so, is really a piece of a stem — a transformed branch ; and 

 tlie characters by which we prove this, are in the same way ap- 

 plicable to all kinds of rootstocks and similar subterraneously 

 growing stems. We can readily detect in potatoes the eyes, 

 which in their first pushing in spring become little green leaf- 

 buds ; if we examine the tubers during the period of their for- 

 mation we find a little membraneous scale covering the spot where 

 the eye is afterwards formed : this scale is a rudimentary leaf. 

 On the turnip or carrot the bud or buds are all assembled at the 

 upper end, the region where the stem and root, ascending and 

 descending growths, set out in opposite directions. 



It is a rule in physiological botany that buds, in general, natural 

 cases, make their appearance only at the points of stems and 

 branches, or in the corner (axil) which the upper side of a leaf or 

 leaf-stalk makes with the stem from which it arises. If thei'e are 

 no leaves there are no side-buds, if no side-buds no branches. 

 This leads us then to a means of scientifically distinguishing 

 roots from rootstocks and the like (which is to say, practically, 

 organs which cannot be multiplied by cuttings from those 

 which can), namely, we can distmguish the stem-structure dis- 

 guised under the form of a root by the presence of scars of leaves, 

 or membraneous or fleshy scales representing leaves ; and while in 

 a great many cases we are already tielped by the presence of buds 

 in the axils of those scars or scales, favourable conditions applied 

 to the rootstock will bring them out if undeveloped. The absence 



