274 M. E. Germain de Saint-Pierre on the Morphology 



The opinion of Guettard (1734<) that these organs formed an 

 appai'atus of secretion, was combated by DeCandolle (1826), who, 

 as well as E. Meyer, believed that the lenticels were the rudi- 

 ments of the adventitious roots. M. Hugo Mohl in his turn 

 (1832-1836) has shown that DcCandolle's opinion was ill- 

 founded, and ascertained that the production of the lenticels is 

 analogous to that of cork, with this difference, that cork is the 

 result of the hypertrophy of the suberose layer of the bark, and 

 that the lenticels are produced by the hypertrophy of a deeper 

 layer, the herbaceous layer. Lastly, M. Unger (1836) thought 

 he recognized a sort of analogy between the lenticels and the 

 soridia of the Cryptogamia, the utricles of cellular tissue which 

 constitute the corky mass of the lenticel appearing to him to be 

 analogous with the spores or propagida. The same observer 

 regarded the lenticels as the result of a deformation of the sto- 

 mata ; and Du Petit-Thouars, who had given an analogous opi- 

 nio)!, considered them to be intended for effecting a sort of com- 

 munication between the external air and the cellular or amy- 

 laceous layer of the bark. The great diversity of opinion in 

 so many distinguished observers, regarding a structure appa- 

 rently so simple and so accessible to study, determined me to 

 undertake some new researches, a summary of which I laid before 

 the Societe Philomatique in 1849 ; I have since continued my 

 series of observations upon this subject, and now lay the results 

 before the Academy. I have chosen for the subjects of my obser- 

 vations three trees in which the lenticels present essential differ- 

 ences of form, — namely the Birch {Betula alba), the Elder (/Sam- 

 bucus nigra), and the suberose variety of the Elm {Ulmus cam- 

 pestris) . 



In the Birch the first state of the lenticel is an epidermic 

 gland of very simple structure. During its period of vitality 

 (on the young branch) this gland secretes a gummy resinous 

 nuitter ; it then dries, splits up and becomes destroyed, leaving 

 in its place a brownish fissure through which the subjacent cel- 

 lular tissue protrudes. It is this cellular tissue which constitutes 

 the adult lenticel, and M. Unger, who examined these glands, 

 did not follow their development as far as the true lenticular 

 period. In this particular case, it cannot be denied that the 

 name of lenticular glands applied by Guettard to the lenticels is 

 correct ; but it can only apply at the period when the prepa- 

 ratory organ of the lenticel exists alone, and when the lenticellar 

 mass docs not yet exist. 



On the e])iderinis of very young branches of the Elder, we 

 may observe stomata and epidermic elevations or short hairs 

 with broad bases. The stomata do not undergo any ulterior 

 change of form ; they are tnerely ol)literatcd in proportion as the 



