Vegetable Physiology. 367 



ces Naiurelles" " sur les Lenticelles des Arbres et le developpement des 

 racines qui en sortent" 



It has been supposed that, from a cutting of a tree, for example, the 

 roots appear indifferently from all points of the bark: but this assertion 

 M. De Candolle declares to be incorrect; they are all, without exception, 

 protruded from small reddish, oval spots, which M. Guettard has named 

 " glandes lenticulairesj" but of which the functions were never known ? 

 To these spots our author has given the name of Lenticelloe, (or iea- 

 ticelles.) 



The experiments were made principally, but not solely upon the Wil- 

 low, in which the following facts were observed. A branch of the Salix 

 bicolor, cut from the parent plant, was placed in a bottle of water, and ex- 

 posed in a stove to a heat of 12 or 13 degrees of Reaumur. The water 

 was presently visibly absorbed, and this absorption was the more rapid, in 

 proportion as the roots were developed. The first sign of vegetation was 

 apparent in the gemmae, or leaf-buds, which became slightly swollen : — 

 soon after, the little oval spots above alluded to began to swell; — the 

 roots were protruded, and then the developement of the gemmae became 

 more decided. The gemmae of the lower part of the branch, and which 

 were consequently nearest to the water, and those at the summit, which 

 of course were farthest from the water, were those which showed the ear- 

 liest signs of vegetation. These appeared in two fixed situations. One 

 set, and that the first to be developed, have their origin from the axils of 

 the old leaves ; they are always solitary, and are the only ones where the 

 branch is uninjured, and when there only remains the scar of the old 

 leaf. The other set, which vegetate more readily, appear when some small 

 lateral branch has been cut away, or that of the original gemmae is cutout 

 or destroyed. Then these develope themselves regularly, two in number, 

 one on each side of the point or scar where the injury has occurred. All 

 the gemmae have, in the beginning, a decidedly ascending direction, and a 

 green colour ; they originate in the woody body, but less distinctly so than 

 the root Their form is that of a sharp and slightly compressed cone ; 

 they divide in two, as it were the covering formed by the epidermis, and 

 present to the eye at once the rudiments of the branch and of the 

 leaves. 



The developement of the roots takes place in the following manner. 

 The lenticular disc, which, in a state of repose, was almost flat, swells and 

 bursts, often into four irregular lobes, and the epidermis is carried up at 

 the extremity of the root. Beneath this, a white, apparently amylaceous 

 matter is seen, from beneath or from the side of which the cylindrical fili- 

 form root is protruded, spongy and soft at the extremity, itself always of a 

 pure white, never becoming green by the action of the solar rays. From 

 these observations upon the nature of the lenticellae, and from tracing the 

 more complete developement of the roots, our author has come to the fol- 

 lowing conclusions upon this interesting subject :■— 



\stly, That the lenticelloe {glandes lenticulaires of Guettard) bear the 

 same relation to the roots which the gemmae or leaf-buds do to the young 

 branches,— that is to say, that they are points upon the stem, where pre- 



