m] 



BARBER-FRUITS AND SEEDS OF CUCURBITACEAE _ 285 



cell laver. In the many fruits I have examined, however, the meso- 

 carp does not show any great differentiation. The outer layers consist 

 of rather small thin-walled cells with intercellular spaces. 



ze of the cells. 



p differs from 



esocarp 



M - 



in the outer mesocarp. The bundles, isolated sieve tubes, and latex 



lout the mesocarp, are of the type already 



tubes, „ __ & 



described. 



Cucurbita. 



™'f— The elongated, thin-walled cells of this layer 



remain with the mesocarp and are not attached to the seeds as in 



__ (figs. 10, 12-14).— Seeds for study should be taken 

 directly from the fruit, as in drying they usually lose their outer 

 walls. 



1. Epidermis {fig. 12, ep).—The prismatic cells are radially 

 elongated to 160 /* on the sides of the seed and 260 /x at the edge. In 

 surface view they are polygonal, transversely elongated, and arranged 

 *ide by side in rows. The outer and inner walls are thickened, the 

 outer having in addition a cuticle, while the radial walls are very 

 thin, with the characteristic thickenings on only the side walls. 

 Each thickening consists of a single straight rod, broadened at the 

 base and tapering rather abruptly into a blunt almost rounded poin 

 j^t within the cuticle. Von Hohnel,^ in the year 1876, described 

 these rods as consisting of two different layers; Fickel," the same 



" ' and Harz,** although quoting Von Hohnel, 



year. 



Pictured three. Mv 



ment. 



distinguished 



tractive- power and by staining. The inner layer, which gives tne 

 c °lor reaction for lignin, shows the strongest refraction; this is su 

 ^nded by a thin layer of cellulose (blue with iodin and su tun 

 ***) of rather weak refractive power; and this in turn is inclosea 

 * a broader, scarcely visible, second laver of cellulose (also taking 

 j he blue stain). Tangential sections show the arrangement ot 

 a >ers and the elliptical appearance of the cut rods. 



13 r -° c - cit., footnote 3, p. 330. *5 Loc. cit., footnote 7, p- 773- 



HLoc - dt., footnote 2, p. 742. 



