160 APPENDAGES. 



as a general principle, that except in cases of necessity, 

 no marks of specific distinction should be drawn from 

 them. They enable us by observing the peculiar ar- 

 rangement which they assume in some of the Mints to 

 discriminate between species, which we should other- 

 wise be apt to confound. Nor is it uncommon for wri- 

 ters to notice as one of the striking features of the plants 

 they describe, whether it be pubescent or not ; that 

 term being employed to express the different kinds of 

 hairs which have been enumerated in the present 

 section. 



5. GLANDS. 



» 



These are minute organs of various forms usually 

 attached to the leaf or its foot stalk. They occur in 

 the substance of the leaves of the Myrtle, Lemon, and 

 common St. Jobn's-wort, causing them to appear dot- 

 ted when exposed to the light. They occur on the pe- 

 tioles of the Nectarine, Snow-ball, and Passion-flower, 

 between the serratures of the leaf in the Almond, and 

 on its superior surface in the Sun-dew. In the latter 

 they are filiform, and tipped with a clear transparent 

 secretion, which glitters like dew in the sun. In 

 Roses, Fig. 59, particularly in the Moss Rose, these 

 glands are elevated on a slender stalk, and contain a 

 secretion, which communicates to many species of that 

 interesting family of plants, their peculiar and delight- 

 ful perfume. Glands sometimes furnish marks of spe- 

 cific distinction, to which it is often convenient and 

 sometimes necessary to resort. They enable us to 

 discriminate betwixt the Almond and the Peach, the 

 leaves of the former being glandulous while those of 

 the Peach are not. 



