1894.] NEW-YORK MICROSCOPICAL SOCIETY, 15 



in diameter, nearly consolidated by internal deposit, giving a 

 darker hue and firmer texture to that portion of the structure 

 and marking the cessation of the periodical growth of the organ- 

 ism; and so standing strongly contrasted with the immediately 

 superimposed layer of thin-walled, larger cells which mark the 

 periodically resumed activity of growth. In the ivory nut the 

 cells are also somewhat lengthened, but, instead of lying parallel 

 with the axis, they radiate from the axis, and all extend outward 

 toward the dark outer surface and normal to its curve. The cells 

 do not usually overlap each other, but with remarkable uniformity 

 they lie side by side, and meet each other end to end. And the 

 appearance of rings and bands is caused by dense clusters of 

 tubules at the ends of these cells, the members of one cluster 

 accurately meeting the members of another cluster from the ends 

 of adjoining cells, the extremities of the approaching tubules, 

 however, always being separated from each other by the middle 

 lamella between two adjoining cells. These clusters are so dense 

 and are so regularly arranged, on account of the usually regular 

 position of the cells side by side, as well as end to end, that, by 

 contrast with the portion of the cell intermediate between the 

 ends — which intermediate portion, however, is also well furnished 

 with tubules — the transverse section shows attenuated but un- 

 broken, daikened circles sweeping around the axis. 



Description of Plate 38. 



Fig. 1.— Longitudinal section of two entire cells of the endosperm of Phytelephas, 

 with four extremities of adjoining cells, meeting end to end. The cells are split longi- 

 tudinally and cleared of cell contents. The darker shaded, portions represent the upper 

 surface of the section, showing the thickness of the cell walls. The lighter portions rep- 

 resent the semi-cylindrical cavity of the cell, like a minute trough, and also many of 

 the tubules, which lie near the upper surface of the section and pass outwardly to the 

 lamella or boundary of each cell. The small circles represent the openings of such 

 tubules as are passing downward at various angles through the remaining thickness 

 of the section. Many of the tubules at the ends of the cells are cut off at various lengths 

 by the plane of the section. 



Fig. 3.— Transverse section of a number of cells of the endosperm of Phytelephas, 

 cleared of cell contents and showing the polygonal outlines. The plane of the section 

 passes through the clusters of tubules at one end of the cells. The shaded portions 

 represent the thickened cell walls, and the clear spaces the contracted lumen of this 

 region of the cells. 



Fig. 3.— Section of the endosperm of Smilacina, with its irregularly globular or ellip- 

 soidal cells, cleared of cell contents. The darkest shaded portions represent those 

 portions of the cell walls which rise directly upward to the upper surface of the section,, 

 and which, therefore, exhibit at best advantage the thickening of the cell walls and the 

 abundance of tubules. 



The three sketches are all of the same magnification— 250 diameters. 



