4 Researches respecting the 



De Saussure found that the covering of leaves, to whirh 

 botanists have given the name of" epidermis, is not a simple 

 membrane, but a real bark composed of three distinct parts; 

 namely, an epidermis properly so called, a cortical reticula- 

 tion, and cortical glands *. 



He defines the epidermis in the following words f : — ^' It 

 is an exceedingly tine membrane, always transparent and 

 colourless, in which no fibre, no pore, and no organiza- 

 tion can be discovered ;" though he allows that this mem- 

 brane opens opposite to absorbent and excretory vessels. 



Hedwig gives the name of pellicle of the leaves to what 

 Saussure calls their bark. The cuticular lymphatic vessels 

 of the former compose the cortical reticulation of the latter; 

 and the evaporating po?-es or conduits of Hedwig are the 

 cortical glands of Saussure. In regard to the epidermis, as 

 this author does not mention it, there is reason to believe 

 that he has confounded it with the pellicle J. 



To enable the reader to comprehend better m hat I have 

 to say in regard to the epidermis, I shall define what I mean 

 by utriculce, as I consider this definition necessary to pre- 

 vent misconception. 



The utriculiE are membranous vesicles filled with a par- 

 ticular juice, and contiguous to each other, in a greater or 

 less extent of their suiiace, according to the form whicli 

 they affect. The utriculas constitute the greater part of 

 leaves. They vary in their form and size ; some of them 

 being round, elongated, prismatic, or irregular. 



All leaves seem to have a bark or exterior covering de- 

 stined to contain the parenchyme and the vessels. In se- 

 veral plants indeed, and particularly the orchis, this kind 

 of bark is seen to separate itself spontaneously by the effect 

 of a peculiar alteration in the leaf. The surface of the 

 leaves may also be frequently removed by employing cau- 

 tion : some then think they see the epidermis in this fine 

 pellicle; and they are the more convinced of it, as they 

 compare it to that of animals. But if this pellicle 1)« 

 examined with attention, it will l>c found, as I have alv/avs 

 seen, that it is formed by the exterior stratum of the utri- 

 cujse, the lateral faces of which are contiguous. I shall, 

 however, except the leaf of the J'ritillaria §, from which 



'■■ Observations sur i'Ecorce des Fcuilles et des Petales; Geneve 176 j. 



•f- Chap. V. page 94.. 



J SainmlunjT seiiitr zerstreuten Abhandlungen. und Beobachtungcn 

 iibcr Botanischc-occonoinische Gcgcnstsende D. I. Hedwigij I^eipsic 

 1790- 



§ Friiillaria regidis Linn. 



T was 



