1906] CHAMBERLAIN—OVULE OF DIOON 339 
and Scorr (13) and illustrated in their fig. 26. The rest of the tissue 
on each side of the abscission zone consists of large, elongated cells, 
forming a loose parenchyma with irregular intercellular spaces like 
those of the abscission zone, except that the spaces are larger. 
Vascular system of the ovule——The distribution of the vascular 
system is easily traced by cutting off the petiole of the sporophyll under 
water and placing the cut end in an aqueous solution of eosin. The 
vessels become filled with the solution in a few minutes. For study- 
ing the course of the bundles in the ovule itself, it is better to cut the 
ovule just below the abscission layer. While the fluid does not always 
penetrate the ultimate tracheids, the course of the bundles is sharply 
marked, as may be seen in figs. 7-9, which are photographs of ovules 
treated in this way. For studying the transverse distribution of 
bundles, series may be obtained very rapidly by cutting sections of 
ovules treated with eosin and simply placing the sections in order 
upon a sheet of paper. The abundant mucilage causes them to 
adhere firmly, and the bundles appear as bright red dots. 
A transverse section of the petiole of the megasporophyll near the 
axis of the cone shows about seven bundles, arranged in a straight 
line. Two of these bundles, one at each end of the row, are usually 
larger than the others, and develop into the vascular systems of the 
ovules. The other bundles branch repeatedly, so that in the widest 
part of the lamina of the sporophyll a transverse section shows about 
thirty bundles, still arranged in one straight line. The outer bundle 
forks once as it passes to the ovule, so that a transverse section just 
below the abscission line of the ovule shows two bundles. From each 
of these two bundles a branch passes toward the outer fleshy layer of 
the integument, and another branch toward the inner fleshy layer, 
thus giving rise to an outer and an inner vascular system with the 
stony layer lying between them (fig. 10). 
The bundles which supply the outer fleshy layer of the integument 
branch several times before they reach the level of lower limit of the 
stony layer, but from this point they extend to the micropyle with no 
branching at all (fig. 7). The number of these bundles in vigorous 
ovules varies from 10 to 17, with 14 as the most frequent number; 
in abortive ovules 12 and 1 3 are the most frequent numbers. In 
very cone there are some abortive ovules, and it may be that an 
