2 4 I 
Compound Rays in the Lower Dicotyledons. 
Fig. 1 8. Abuts japonica. Transverse section of a small twig, showing a somewhat specialized 
form of central cylinder in which long sheets of aggregated tissue, in relation to the leaf-traces, have 
produced a segmented appearance of the stem, x io. 
Fig. 19. Alnus japonica. Transverse section of the stem below the node, showing a leaf-trace 
bundle and associated tissue from which the vessels are gradually disappearing, x 40. 
Fig. 20. Quercus alba. Transverse section of the stem, showing aggregating tissue associated 
with a lateral leaf-trace, x 40. 
Fig. 21. Alnus japonica. Transverse section near the node, showing the leaf-trace just 
starting out to the leaf, the foliar gap left in the primary cylinder, and the aggregating tissue related 
to the leaf-trace, x 40. 
Fig. 22. Corylus rostrata. Transverse section of the stem, showing the relation of an aggregate 
ray to the lateral leaf-trace, x 40. 
Fig. 23. Alnus japonica. Transverse section above the node, showing the relation of the 
aggregate ray to the persistent foliar gap in the primary woody cylinder, x 40. 
Fig. 24. The same. Tangential section of the wood, showing the aggregating tissue which 
occurs above and below the lateral leaf-traces, x 40. 
PLATE XVII. 
Fig. 25. Quercus alba. Transverse section of a small branch, showing the five small sunken 
segments which are depressed by the retarding influence of the approximated lateral leaf-trace rays 
upon the growth of the stem, x 10. 
Fig. 26. Quercus virginiana. Transverse section of the stem, showing the aggregate rays 
which appear to originate at some distance from the pith, x 12. 
Fig. 27. Quercus velutina. Transverse section of the stem, showing a sunken segment and 
the retarding influence of the aggregate rays upon the growth of that portion of the stem, x 15. 
Fig. 28. Quercus virginiana. Tangential section of the wood, showing the small amount of 
aggregating tissue that is associated with the lateral leaf-trace in the first- formed wood of the stem, 
x 60. 
Fig. 29. Quercus velutina. Transverse section of the stem, showing two aggregate rays related 
in origin to a single lateral leaf-trace, x 20. 
Fig. 30. Quercus virginiana. Tangential section of the wood at some distance from the pith, 
showing a portion of the long aggregate ray that is associated with the lateral leaf-trace, x 60. 
R 
