634 CONSERVATIVE ORGANS. [LECT. XI. 



resemble the papillary glands in some degree, each 

 being a slight elevation with a depression in the 

 centre; and it is probable that these are the secret- 

 ing organs, and, severally, communicating with 

 the excretory pore, pour the fluid they secrete 

 into it; whence it is exuded: and acquires its 

 dark colour by exposure to the atmosphere. 



3. The scaly gland, glandula squamom*, re- 

 sembles a minute scale attached to the surfaces of 

 the leaves on which it is found, as, for instance, 

 on that of Rhododendron punctatum. The under 

 surface of this leaf is covered with glands of this 

 species, which appear, when viewed with a good 

 glass, like small brilliant detachable scales, white 

 and shining round the edge and dark in the centre 

 (Plate 9, fig. 29. A. a.). When one of these scales is 

 placed under the microscope, the white border is 

 found to be beautifully fluted (fig. 29. B. b. c.), and 

 lying flat upon, but not attached to the surface of 

 the leaf ; and to be the loose margin of the scale 

 covering the gland, which appears to be a slightly 

 elevated papilla, discharging its secretion by se- 

 veral excretory pores which open upon the surface. 

 The real shape of the gland, however, is that of 

 an inverted cone, of which the scale is the base. 



* I am surprised that the error of Guettard, who gave 

 this name to the thin scale which covers the fructification of 

 Ferns, has been copied by Mr. Keith in his System of Physio- 

 logical Botany. See vol. .i. p. 69. 



