2IO BOTANICAL GAZETTE [September 



i mm 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. 20). From this 

 weaker lobe a very small strand passes out (D, figs. 21-24, 2( 5, 3°), 

 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, 2Q, 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, b') to form the 

 lateral trace of the cotyledon, the other, a very small strand (a, a'), 

 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 eduel, 

 and Microcycas suggested that the smaller bundles (D, a, a') were the 

 mates of the larger ones on the side of the cotyledon (C, b, b') , 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 is 

 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 Ceratozamia 

 embryos developed on the clinostat, and fig. 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. 30 

 at z. This bundle has its origin in a small group of cells (cb", fig. 32) 

 in the outermost layer of cambium. It is about o.4 mm long and 

 approximately vertical. Its tracheids have only spiral thickenings. 



The foliar bundles (jb) may occur in four groups alternating with 

 the cotyledonary bundles (figs. 21-23, 26, 3°) I but oftener there are 

 only three groups, because of the fusion of two of them or the entire 

 elimin tion of one, on the side of the suppressed cotyledon, when the 

 main bundle (D) is slight or entirely wanting (fig. 26). At first they 

 are all vertical; higher up they branch, and a strand from each group 



