566 Weiss . — The Vascular Branches of 
but of a more complex character, so that more numerous 
branches appear in the transverse section. Of this, however, 
I have not been able to see any trace in such longitudinal 
sections of this type of rootlet as I have been able to examine. 
Unfortunately they were mostly too oblique to allow any very 
definite statement to be made. It will be noticed that in 
Fig. 3, as in the case referred to by Dr. Scott, the tracheids 
increase somewhat in size soon after they are given off from 
the protoxylem, a feature which is not noticeable in the other 
types of rootlets, where the dilated tracheids are only ob- 
servable after the strand has reached the outer cortex. In 
all cases, however, we have that sequence of narrower tracheal 
elements to which Strasburger draws attention (’ 91 ) 1 . He points 
out that in all cases the narrower absorb water from the wider 
elements. In both categories of Stigmarian rootlets, therefore, 
the flow of water would take place from the wider tracheids of 
the cortex to the narrower protoxylem elements of the central 
cylinder. The rootlet represented in Figs. 3 and 4 shows 
very clearly the wider spiral tracheids of the cortex, similar 
in general features to those of the rootlets in Figs. 2 and 5 « 
These tracheids appear, however, in the second type of rootlet 
to be differentiated into narrow ones running longitudinally in 
the rootlet and wider transverse ones. This arrangement 
reminds one forcibly of the terminal ramifications of the 
vascular bundles in a Monocotyledonous leaf as figured by 
De Bary for Zea Mais 2 . 
The position >of the spiral tracheids is also different in 
this last rootlet from that described for the other rootlets. 
It will be seen in Figs. 3 and 4 that the tracheidal elements 
of the cortex are here found externally to the cells with dark 
cell-walls. Whether these were in all cases thick walls, or 
whether their constitution caused a discolouration of the cell- 
wall substance, it would be difficult to say ; but the presence 
of the tracheids on the outside of this layer of cells would 
suggest that in this rootlet they might be less permeable 
1 Strasburger, E., Leitungsbahnen, p. 873. 
2 De Bary, A. (’ 84 ), Fig. 175, p. 371. 
