210 BOTANICAL GAZETTE [SEPTEMBER 
1™™ above the upper terminus of the protostele, the xylem is grouped 
sometimes in four conspicuous mesarch lobes, but oftener in three 
prominent ones and a fourth weaker one (D, fig. 29). From this 
weaker lobe a very small strand passes out (D, jigs. 21-24, 26, 30), 
and in some cases it branches, but is lost in the cortex. From the 
lobe diametrically opposite, the median strand of the cotyledon 
(C, figs. 21, 24, 25, 29, 30) enters that organ; and from each of the 
other two angles or lobes a strand passes out (A, B) and branches, 
one member in each case bending tangentially (b, 0’) to form the 
lateral trace of the cotyledon, the other, a very small strand (4, @’), 
either fusing with the leaf traces or dying out in the cortex. This 
cotyledonary node is represented in cross-section in the diagram 
(fig. 24). | 
Comparison with the same node in Zamia, Cycas, Dioon edule, 
and Microcycas suggested that the smaller bundles (D, a, a’) were the 
mates of the larger ones on the side of the cotyledon (C, }, ¥), and 
that the second cotyledon was suppressed. The cause of the sup- 
pression was indicated by the long-continued one-sided presentation 
to gravity during germination, and the fact that the cotyledon 's 
always on the under side. It was with the intention of testing these 
surmises that the experimental work already recorded (3) was under- 
taken. Fig. 25 represents the cotyledonary node in Ceratozami@ 
embryos developed on the clinostat, and jig. 13a a transverse section 
of their cotyledons. 
Although the stem contains several layers of extrafascicular 
cambium (cb, fig. 32), I have not been able to find in two-year-old 
plants any anomalous thickenings except the solitary bundle (fig. 33) 
whose position in the base of the cotyledon is indicated in fig. 3° 
at z. This bundle has its origin in a small group of cells (c”, hg: er 
in the outermost layer of cambium. It is about 0.4™™ long ” 
approximately vertical. Its tracheids have only spiral thickening» 
The foliar bundles (fb) may occur in four groups alternating 
the cotyledonary bundles (figs. 21-23, 26, 30); but oftener there as 
only three groups, because of the fusion of two of them or the a 
elimin *tion of one, on the side of the suppressed cotyledon, when t 
main bundle (D) is slight or entirely wanting (jig. 20)- At first they 
are all vertical; higher up they branch, and a strand from each grouP 
