On some retnarkable Plants in the 



crenato-serrata cum mucronulis adpressis, semi-conduplicata, 

 coriacea, venis secondariis arcuatis reticulatim nexis ; ver- 

 natio conduplicato-involuta. 



simplest theoretical form of leaf I take to be entire and cellular, the first 

 step in complication resulting from the extension of an axile vein. And 

 as reticulating veins are the last that make their appearance, it may 

 be suggested that a Dicotyledonous leaf will at some period of its de- 

 velopment present the appearance characteristic of a Monocotyledonous 

 leaf. 



The last observation I have to make refers to the Pitchers or Ascidia 

 of Nepenthes: these, from observations on their development, I consi- 

 der to be modifications of excurrent midribs. That such is their nature 

 at first will, I imagine, on examination, be readily allowed. In this 

 explanation the part which is developed like an ordinary lamina, looks 

 like an ordinary lamina, and which performs the proper functions of 

 an ordinary lamina, is the lamina ; the apex of the excurrent midrib is 

 the subulate process at the base of the lid, and the lid is a special de- 

 velopment of the upper margin of the originally simple foveola or 

 cavity, subsequently the pitcher. This explanation differs from that of 

 M. Link, Dr. Lindley and Professor Morren, which agree in consider- 

 ing the foliaceous expansion as a dilated petiole — differing substanti- 

 ally, however, in the nature attributed to the pitcher itself and its 

 lid. That hypothesis, indeed, which considers the lid to be the lamina 

 or blade of the leaf, would, in my opinion, be much more consonant with 

 appearances if the lid were considered as resulting from marginal 

 cohesion of a folium unijugum. 



I do not extend the above explanation to such instances as Sarrace- 

 nia etc. still less, perhaps, to species of Disckidia, in which the 

 pitcher can be traced, through a series of modifications, to the lamina 

 of the leaf itself. In the instances presented by the last genus, whether 

 the leaf be completely convolute, or merely concave, it always appears 

 to perform some function connected with the radicular fibres. 



In Nepenthes distillatoria the species examined, the apex of every 

 leaf will be found to present the cavity, which is to be subsequently, 

 sooner or later, the ascidium. This, together with the fact that in N. 

 ampidlaria the leaves of the flower-bearing branches have no developed 

 ascidia, these being limited to the short procumbent humifuse branches, 

 may be considered perhaps an objection to the views of Mr. Link of their 

 being floriform organs. 



