27 lAnnean Society. [Dec. 2, 



separation of the cells. The green parenchyma is almost entirely- 

 confined to the upper half of each tube, and ceases abruptly with- 

 out any apparent cause. It consists of a single layer of colourless 

 oval or roundish sacs, arranged with the most beautiful regularity in 

 longitudinal lines extending from the base to the apex of the leaf, 

 and corresponding with the bodies of the cells forming the cutis and 

 not with the intervals between them. The stomata are confined to 

 the under halves of the leaves, or to that portion of the tubes which 

 is destitute of parenchymatous tissue. 



In the terrestrial species the structure of the leaves is essentially 

 the same, but the number of longitudinal tubes is increased, and va- 

 ries from six to twenty, the central ones only reaching the apex of 

 the leaf. The longitudinal divisions between these tubes are marked 

 externally by corresponding depressions, and each is furnished with 

 a vascular fascicle similar in structure and position to that of E. se- 

 taceum. The parenchymatous cells are arranged with less symme- 

 try than in that species, and are not so completely confined to the 

 upper surface ; and the lower surface abounds with stomata. 



The sheaths which envelope the base of the peduncle have in all 

 the same organization, which is exactly that of the leaves of the ter- 

 restrial species. The peduncles are also composed of tubes, circu- 

 larly arranged; they are marked externally with elevated whitish 

 lines, which (in the living plant) have a slightly spiral direction 

 from left to right, and correspond to the longitudinal septa. The 

 tubes meet in a cellular axis, around which the vascular fascicles are 

 arranged in corresponding number; and the septa form so many 

 spokes consisting of more or less elongated cellular tissue, which in 

 one species (£. WallicManum) ajjproaches in density to woody fibre. • 

 The parenchyma within the tubes is disposed with less regularity 

 than in the leaves and sheaths, and their outer green parietes abound 

 with stomata. With one exception, the number of tubes in the 

 sheaths bears an exact relation to that in the peduncles of two to one. 



The author describes the cavities existing in some Alismacece, Pon- 

 tederia, Cyperacece and Nelumbinece, as originating in the same man- 

 ner as the chambers in the tubes of Eriocaulon, from the interposi- 

 tion of cellular septa perforated by fissures caused by the separation 

 of the cells and not by any inteiTuption of the membrane. In Pon- 

 tederia dilatata raphides are found in great abundance in cells at- 

 tached to the septa in such a manner as to project at right angles 

 beyond either surface, and to occupy the spaces left by the separa- 

 tion of the ordinary cells. The same disposition occurs in some 

 Aroidece. 



