182 ORGANOGRAPHY. 



performs in such a case all its functions. To such a petiole the 

 name oi phyllodium or phyllode has been applied. In some cases, 

 as in Acacia heterophi/l/a, the phyllocle is terminated by a true 

 blade (fig. 366), and its nature is thus clearly ascertained, but 

 in other instances no blade is produced (fig. 365), and such 

 plants arc commonly termed leafless. These phyllodes may be 

 distinguished from true blades, not only by the frequent produc- 

 tion of a lamina (fig. 366), but also by other circumstances. 

 Thus, — 1st, By their venation, Avhich is more or less parallel 

 (fig. 366) instead of reticulated, as is the case generally iu 

 Dicotyledonous Plants in which they alone occur. 2nd, By 

 their being placed nearly or quite in a vertical direction — that is 

 turning their margins instead of then- surfaces to the earth and 

 heavens. And 3rd, By their two surfaces resembling each other, 

 whereas in true blades a manifest difference is commonly observ- 

 able between the upper and lower surfaces. Trees presenting 

 this character in their petioles are very common in Australia, 

 and give a very peculiar character to the vegetation of that 

 country by the singular distribution of light and shade which 

 they produce, as was first noticed, and the cause ascertained by 

 that most acute botanist Robert Brown. 



Besides the true phyllodes thus described, there are how- 

 ever some others, which are generally considered as such by 

 botanists, which do not possess such well marked distinctive 

 characters, as the leaves of some species of Kanunculus, &c. 

 In these phyllodes the direction is horizontal as in true blades, 

 and in some other respects they resemble them ; they have how- 

 ever parallel venation instead of reticulated, and belonging to 

 Dicotyledonous Plants, this character will suffice to distinguish 

 them, as it is now become the general rule of botanists to con- 

 sider all organs occupying the place of leaves among Dicotyle- 

 dons which are not reticulated, as phyllodes. 



Ascidia or Pitchers. — These are the most remarkable of all the 

 anomalous forms presented by leaves. They may be seen in 

 the Pitcher plants, as Nepenthes distitlatoria (fig. 367), in the 

 Side-saddle plant (Sarrncenia purpurea) (fig. 368), in the Dis- 

 chidia Rafflesiaiia, and in many others. These curious organs 

 may be either formed from the petiole or the blade of the leaf. 

 Thus, in Sarracenia (fig. 368), the pitcher appears to be pro- 

 duced by tlie folding inwards of the two margins of a phyllodc, 

 which unite below, and form a hollow body or ])itcher, but which 

 arc still separate above, and thus indicate its origin. Tlie origin 

 of the pitcher from the pliyllodc is however ])robably best seen 

 in a species of IIeliami)liora (fig. 369) described ])y Mr. Bcntham, 

 in which the union of the margins of tlie i)hyllodc is oven less evi- 

 dent than in the Sarracenia. In the Nepenthes (fig. 367), the 

 petiole first cx]ian(ls into a phyllodc, then assumes the ajjpearance 

 of a tendril, and ultimately forms a pitcher, which is dosed above 



