— 143 — 



difficult to trace them. However, the woody ring is here in 

 reality built up of bundles. In Hypericum and Potentilla the bund- 

 les consist only of Protoleptom while the cambium forms the xy- 



Fig. 3. Euonymus latifolia: Transverse section of a part of the central cylinder; 

 two young vascular bundles; only phloem can be distinguished; X c - 550. 



lem. The protohadrom here is often rudimentary. Perhaps one 

 might object that isolated bundles of protoleptom do not indicate 

 separate vascular bundles, leptom always beginning to develop 



Fig. 4. Linum austriacum: Transverse section of a part of the central cylinder; 

 3 young bundles. X c. 550. 



in small groups in the continuous cylinder as well as the proto- 

 hadrom. With regard to the Rosaceæ — which family plays an 

 important part in the American investigations — it is evident that 



