INTRODUCTION. XXIH 



CupuliferoD have the principal lateral veins running straight out from 

 the midrib to the margin ; Betuline?e are distinguished by this among 

 other characters from Salicinese ; and the same peculiarity separates 

 the genuine genera of Dilleniacete, called Delimacese by Decandolle, 

 from those of which Hibbertia is the representative. — Leaves which 

 contain reservoirs of oily secretions, indicated by the presence of 

 pellucid glands within their substance, are almost always universal 

 in a given order. Thus, Myrtacese, properly so called, (with the 

 exception of the paradoxical pomegranate,) are distinguished by 

 these glands from Melastomaceae ; in one genus of which, however, 

 (Diplogenea,) slight traces of them are to be found : they are-present 

 in all Aurantiacese ; by this character Winterer are distinguished from 

 Magnoliaceae, Amyridese from Connaraceae, &c. &,c. In the orders 

 Phytolaccese, Petiveracea, Labiatse, and Zygophyllese, there are, how- 

 ever, genera with and without pellucid dots. 



At the base of some leaves are frequently found little membranous 

 or foliaceous appendages called STiPULiE, which are in fact leaves 

 in an imperfect state of developement. Their presence may therefore 

 be understood to indicate a peculiar degree of composition in the 

 leaves to which they belong, and they really indicate affinities in a 

 very remarkable manner. In studying them, however, care must be 

 taken not to confound genuine foliaceous appendages, to which alone 

 the name of stipulse properly appertains, with dilatations, or mem- 

 branous or glandular processes of the petiole, such as are found in 

 Ranunculaceai, Grossulaceee, Apocyneae, Umbelliferee, and others. 

 The presence of stipulaB is universal in Cinchonaceae, which are thus 

 distinguished from Stellatse, in Betulinese, Salicineae, Magnoliacea?, 

 Artocarpeae, and many others : a particular modification of them, 

 called the ochrea, is the peculiar distinction of Polygonege ; and they 

 are universally absent in Myrtaceae properly so called, Guttiferee, 

 Gentianese, Malpighiaceee, and many others. The orders Cistineje, 

 Saxifrageae, and Loganiese, are among the very few cases in which 

 genera exist both with and without stipulee. (See Von Martius 

 Nov. Gen. et Sp. 2. 135.) 



The little starved leaves found at the base of many flowers, and 

 technically called Bracte^, are rarely employed as distinctions 

 of orders, offering scarcely any modifications of importance. In 

 Crucifer^ they are never present, and in Marcgraaviacesc they are 

 usually hollow, being folded together by their two edges, like the 

 leaves of which carpella are formed. 



Forms of Inflorescence are occasionally, but not often, found 

 characteristic of particular tribes. Thus all Compositae, Calycereae, 

 and Dipsacese, have their flowers in heads ; all Umbelliferee bear 

 umbels ; all Labiatse have axillary cymes called verticillastri ; all 



