176 ORGANOGRAPHY. 



heterophylla, the phyllode is terminated by a true blade {fig. 

 363), and its nature is thus clearly ascertained, but in other 

 instances no blade is produced {fig. 362), and such plants are 

 commonly termed leafless. These phyllodes may be distin- 

 guished from true blades, not only by the frequent production 

 of a lamina {fig. 363) as just mentioned, but also by other cir- 

 cumstances. Thus, — 1st, By their venation, which is more or 

 less parallel ( fig. 363) instead of reticulated, as is the case 

 generally in Dicotyledonous Plants, in which class of plants they 

 alone occur. 2nd, By their being placed nearly or quite in a 

 vertical direction — that is, turning their margins instead of their 

 surfaces to the earth and heavens. And 3rd, By their two 

 surfaces resembling each other, whereas in true blades a mani- 

 fest difference is commonly observable between the upper and 

 lower surfaces. Trees presenting phyllodes are very common in 

 Australia, and they give a very peculiar character to the vegeta- 

 tion of that country by the singular distribution of light and 

 shade which they produce. 



Besides the true phyllodes thus described, there are some 

 others, which do not possess such well-marked distinctive 

 characters, as the so-called leaves of some species of Ramm- 

 cuius. In these phyllodes the direction is horizontal as in true 

 blades, and in some other respects they resemble them ; they 

 have, however, parallel venation instead of reticulated, and be- 

 longing to Dicotyledonous Plants, this character will suffice to 

 distinguish them, as it is now become the general rule of 

 botanists to consider all organs occupying the place of leaves 

 among Dicotyledons 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 distillatoria {fig. 364), in the 

 Side-saddle plant {Sarracenia purpurea) {fig. 365), and in many 

 others. These curious organs may be either formed from the 

 petiole or the blade of the leaf. Thus, in Sarracenia {fig. 365), 

 the pitcher appears to be produced by the folding inwards of 

 the two margins of a phyllode, which unite below, and form 

 a hollow body or pitcher, but which are still separate above, 

 and thus indicate its origin. The origin of the pitcher from 

 the phyllode is, however, probably best seen in a species of 

 Heliamphora {fig. 366) described by Mr. Bentham, in which 

 the union of the margins of the phyllode is even less evident 

 than in the Sarracenia. In the Nepenthes {fig. 364), the 

 petiole first expands into a phyllode, then assumes the ap- 

 pearance of a tendril, and ultimately forms a pitcher ; this 

 is closed above by a lid, I, called an operculum, which is united 

 to it by an articulation. The lid is here regarded as a re- 

 markable transformation of the blade. This kind of pitcher 

 is looked upon by some botanists as a modification of such 



