ANATOMY AND PHYLOGENETIC POSITION OF BETULACEAE 435 
Fig. 2. Casuarina torulosa. Tangential section of wood showing aggregate 
ray. X 30- 
Fig. 3. Alnus japonica. Transverse section of aggregate ray enlarged in 
vicinity of leaf-trace. X 20. 
Fig. 4. Alnus japonica. Tangential section through aggregate ray and leaf- 
trace. X 25. 
Fig. 5. Alnus mollis. Transverse section of young twig through region of 
node showing aggregate rays, the largest of which is related to a leaf-trace. X 10. 
Fig. 6. Alnus mollis. Transverse section of wood of stem showing only 
uniseriate rays. X 20. 
Fig. 7. Alnus mollis. Transverse section of wounded root showing aggrega- 
tions of rays. X 20. 
Fig. 8. Alnus mollis. Transverse section of part of an old root showing normal 
aggregate rays. X 15. 
Fig. 9. Alnus Yasha. Transverse section through the first annual ring of a 
twig showing aggregations of rays. X 15. 
Fig, 10. Corylus americana. Transverse section in the region of a root-trace 
showing aggregation of rays in relation to the lateral root. X 25. 
Fig. II. Corylus rostrata. Tangential section cut in the vicinity of the root- 
trace showing aggregation of rays. X 25. 
Fig. 12. Carpinus cor data. Transverse section of twig showing aggregations 
of rays. X 10. 
Fig. 13. Carpinus cor data. Transverse section of root showing an aggregate 
ray related to a secondary root. X 15. 
Fig. 14. Carpinus cordata. Transverse section of the same aggregate ray as 
in Fig. 13 enlarged. X 30. 
Fig. 15. Ostrya virginiana. Transverse section through the early annual rings 
showing a persistent tendency to aggregate. X 20. 
Fig. 16. Ostrya virginiana. Transverse section of root showing aggregation of 
rays about the trace of lateral root. (Upper side). X 15. 
Fig. 17. Ostrya virginiana. Transverse section of aggregate ray around trace 
of lateral root, much enlarged. X 30. 
Fig. 18. Betula lenta. Transverse section of root showing aggregation of rays 
in relation to lateral roots. X 30. 
Fig. 19. Betula alba. Transverse section of wood of a twig near the top of 
the tree showing aggregation of rays. X 20. 
Fig. 20. Betula alba var. papyrifera. Transverse section of axis of wounded 
seedling showing traumatic aggregate rays. X 15. 
Fig. 21. Betula alba, var. papyrifera. Part of Fig. 20, more highly magnified. 
X 30. 
Fig. 22. Betula alba, var. papyrifera. Transverse section of twig in region of 
node showing vestigial aggregations related to leaf -traces. X 10. 
Fig. 23. Betula alba, var. papyrifera. Transverse section through reproductive 
branch showing persistence of aggregate rays. X 10. 
Fig. 24. Betula alba, var. papyrifera. Transverse section of root showing 
aggregate ray related to lateral root. X 15. 
