LECT. XT.] CAULINAR AND FOLIAR APPENDAGES. 633 



cells are smaller, more regular than those of the 

 substance of the leaf, and arranged in circles. I 

 have not been able to detect any vessels passing 

 into these glands, nor to discover their excretory 

 pores ; except in the sting of the nettle, which is 

 the excretory duct of a papillary gland. A va- 

 riety of this gland, generally described as a dis- 

 tinct species, under the name lenticular, glandula 

 lenticular is, is found on the surface of the stems 

 of Stripe-flowered Psoralea, P. glandulosa, and 

 of many other dicotyledons. It is a small follicle, 

 which generally contains an oily or a resinous 

 fluid ; and differs from the internal follicular gland 

 only in its situation on the surface. 



2. The compound papillary gland, glandula 

 papillarum composita, is best exemplified as it is 

 found on the leaf of the Stone Pine, Pinus pinea. 

 If we examine the surface of this leaf, with a 

 good magnifying glass, we find that it is streaked 

 with whitish lines, on which are seen small black 

 spots arranged in a regular series (Plate 9, fig. 

 28. A.). Under the microscope each of these spots 

 is discovered to be the excretory pore of a com- 

 pound gland, composed of six distinct glandules, 

 forming a ring or collar (fig. 28. B. a.) around 

 the pore (&.), which generally appears obstructed 

 by minute, dark-coloured, terebinthinous par- 

 ticles ; and is seen to be really a pore, only when 

 the cutis is very carefully raised. The glandules 



