19 1 2] JONES— DI ANT HERA 1 3 



second node, where there has been formed a vascular ring. On 

 passing through this node, we now find a new condition. Instead 

 of the vascular ring breaking into four bundles, two of which fork 

 lower down in the internode, it breaks into four bundles, two of 

 which almost immediately divide, the four forks behaving in the 

 same way, however, as the forks produced at the lower end of the 

 internode of earlier stages (see diagram of path of bundles, fig. 29). 

 This condition is very nearly that which exists in the apex of a 

 mature plant (compare diagram, fig. 2), where the nodal ring 

 breaks up immediately into six bundles, four of which, correspond- 

 ing to the two forked side bundles, are usually smaller than the 

 other two. 



An examination of the lower internodes of this stage (fig. 29) , 

 or of the corresponding internodes of the intermediate stages, 

 shows that there is a tendency from the very first for the side 

 bundles to fork at a slightly higher level in each succeeding inter- 

 node. In the third stage, where these side bundles first 

 there is but a very small amount of parenchymatous tissue inclosed 

 above the leaf traces by these forks, forming small leaf gaps. At 

 each succeeding stage, these gaps tend to be longer when formed. 

 I say tend, for there is considerable irregularity. One of the side 

 bundles may fork about the middle of the internode, while the 

 opposite side bundle of the same internode may not fork until very 

 near the bottom of the internode, or, as before mentioned, may not 



come 



fork at all. 



gradual 



transition from the immature seedling condition found in the 

 earliest stages, and hence lowermost internodes, to the nearly 

 mature conditions found in the uppermost internodes of the 



end 



permanent re< 

 ment, slightly obscured, it is true, by 



thickening. It is comparable in this respect to a fern 

 the earliest formed internodes showing the simple (primitive?) 

 type of structure, the later formed ones showing a gradual transition 

 to the mature type. It must be remembered, however, that in the 

 tern, when the mature structure is once formed, the main axis con- 

 tinues its growth, each succeeding internode having the mature 



