224 E antes . — On Origin of Herbaceous Type in Angiosperms. 
The first step in this process has been the formation of compound rays 
in connexion with the trace. In the next stage whole segments of the cen- 
tral cylinder in relation to the leaf-trace become transformed entirely into 
parenchyma with the exception of the primary wood (which is the trace in 
the stem). Thus there is obtained a stem with alternating segments of 
typical xylem and parenchyma, the latter with tiny groups of typical xylem 
elements on their centrad sides, or, in other terms, alternating large and very 
small bundles, the latter being leaf-traces. The leaf-trace segments, before 
their transformation, were first delimited laterally by transformation of 
xylem in narrow radial bands. This, in stems with thin xylem rings, is 
in itself sufficient to produce the herbaceous structure. When a cylinder is 
thus split up, the cambium ring remains unbroken for some time, the inter- 
fascicular portions actively forming parenchyma. As the plant becomes 
more and more herbaceous these segments of the cambial layer become less 
active and finally disappear. Later, the fascicular cambium, too, is sup- 
pressed, and the highest type of bundle, very small and without secondary 
growth, is formed. Along with this great increase of interfascicular paren- 
chyma goes a gradual disappearance of rays from the diminishing bundles, 
so that the highest type lacks rays completely. Most of these points are 
exemplified by certain herbaceous perennials belonging to the Rosaceae ; 
their two kinds of stems, subterranean and perennial, aerial and annual, 
have proved favourable for such demonstrations. 
The writer desires to express his thanks to Mr. I. W. Bailey for 
opportunity to observe and compare ray development in many woody 
plants, and to Dr. E. C. Jeffrey for material and for suggestions and advice 
during the investigation. 
DESCRIPTION OF PLATE XIV. 
Illustrating Mr. Eames’s paper on the Herbaceous Type in Angiosperms. 
(It is suggested that a hand lens be used in the examination of these figures.) 
Fig. i. Potentilla palustris. Portion of cross-section of prostrate perennial stem, showing 
segment below exit of leaf-trace, x 40. 
Fig. 2. Sanguisorba canadensis . Portion of cross-section of rootstock, showing two bundles 
connected by interfascicular cambium, that on the right consisting in large part of parenchyma. 
X 50. 
Fig. 3. Sanguisorba canadensis . Portion of cross-section of mature aerial stem, showing 
portions of two bundles, with slight evidence of interfascicular cambial activity, x 100. 
Fig. 4. Geum rivale . Cross-section of base of fertile aerial stem, showing dissection of a thin 
central cylinder by leaf-traces, x 15. 
Fig. 5. Potentilla pennsylvanica. Cross-section of rootstock, showing alternating segments of 
xylem and parenchyma, x 12. 
Fig. 6. Potentilla pennsylvanica. Portion of cross-section of rootstock, showing alternating 
segments of xylem and parenchyma, the latter with leaf-traces either passing out, or upon their 
medullary border, x 25. 
