THE PALM-STEM. 13 



spongy mass ; e. g. in Geonema simplicifrons, (Enocarpus 

 minor, Kuntkia montana. In these instances only the 

 smaller cells, forming the boundaries of the vascular 

 bundles, retain the form of regular parenchymatous cells ; 

 the rest, very much enlarged, run out in a radiating 

 direction from the vascular bundles, and form as many 

 stellate rosettes as there are vascular bundles. In other 

 cases, the cells in the central portion of the stem do not 

 attain to such considerable dimensions ; but the tissue 

 is rendered lax by the intercellular passages becoming 

 enlarged into regular air-canals. Calamus forms the 

 transition here, in which large intercellular passages occur 

 between the cells in the middle of the stem ; these, how- 

 ever, still preserve too much of the form of regular 

 parenchymatous cells, and the intercellular passages are 

 still too small, to allow of our properly reckoning this 

 cellular tissue under the so-called compound form. This 

 occurs to a great extent, however, in Astrocaryum gyna- 

 canthmn, vulgare, Mauritia vinifera, and especially in 

 Mauritia armata. Here the cells leave between them 

 large roundish canals, which run in unbroken continuity 

 through long tracts in the stem, so that one can blow 

 smoke through pieces of the stem more than a foot long. 

 At the extremities these canals are gradually attenuated 

 till they become completely closed, for the septa of 

 stellate cells, such as are found in many aquatic plants, 

 in Musa, &c., do not occur in the Palrns. 



Obs. 1. Certain German phytotomists (Heyne, Meyen) have recently 

 sought to distribute the cellular tissue into a great number of subdivisions^ 

 according to the form of the cells ; this appears to me contrary to nature, on 

 account of the abundance of intermediate conditions between all these forms. 

 The above description of the cellular tissue of the Palm-stem may serve as a 

 testimony that the form of the cell stands in no close connexion with its 

 function, and that it depends quite as much upon the form, organization, 

 and position of the adjacent cells and vascular bundles, as on the special 

 nature of the cells. In comparing the stems of different Palms it is un- 

 mistakeable that cells, lying in corresponding places in different species, which 

 have a similar import in the economy of the plants, exhibit wholly different, 

 often variable forms, and it therefore appears quite improper to attach so 

 much importance to the form of the cells. 



