564 Bancroft.—A Contribution to our 
B. ramosa, and B. hirsuta . So far as the foliar trace is concerned, the four 
species form a progressive series from the relatively primitive B . antiqua to 
the tridentate types, R. cylindrica representing an intermediate term. 
B . forensis does not appear to be very nearly related to this group of 
British species. 
5. The Primitiveness of the Stelar Condition , p. 561. 
Typical steles of R. cylindrica show some divergence from the primitive 
condition, whether this is considered to be an endarch or an exarch proto- 
stele, or an asterostele. 
6. The Homology of the Leaf , p. 562, 
The method of separation of the foliar trace in R. cylindrica affords 
support to the view that stem and leaf represent homologous branches 
of a primitively undifferentiated system. 
University College, 
London. 
May , 1915. 
EXPLANATION OF PLATES XXVI AND XXVII. 
fix. = protoxylem ; xi. = inner wood; xo. = outer wood ; amx. — adaxial metaxylem; st. = 
sieve-tubes; fic. — pericycle; e. = endodermis; ic. = inner cortex; me. = middle cortex; oc. = outer 
cortex; l. = lacunae of middle cortex; c. = cavities of outer cortex; rt. — root-trace; It. = leaf- 
trace ; b. — branch stele ; fiar . = parenchyma ; s. = stem ; fi. — petiole. 
PLATE XXVI. 
Rachiofiteris cylindrica , 
Fig. i. A typical a stem, showing the mesarch protoxylem groups, and the slight differentiation 
of the internal wood. Note the somewhat concentric inner layers of the cortex; the thin-walled 
crushed cells composing the outer cortex, and the cavities in this layer, x 32. (From Q 531, Cash 
collection.) 
Fig. 2. A centrarch a stem, x 27. (From K 21 d, University College, London.) 
Fig. 3. A £ stem, showing the small stele, with central protoxylem, and the wide cortex of 
thin-walled cells. At r, a root has just passed out; in the cortex is a small leaf-trace; at /, the 
lacunar structure of the middle cortex is shown, x 27. (From K 21 d, University College, London.) 
Fig. 4. A /3 stem, in which the middle cortex possesses large lacunae. The stele of this stem 
does not show the typical condition, as it possesses two protoxylem groups, x 36. (From Q ro3, 
Cash collection.) 
Fig. 5. An a stem in which the stele is preparing for dichotomy. The branch-stele is slightly 
smaller than the parent stele ; it possesses two protoxylem groups and some adaxial metaxylem (cf. 
Fig. 6, in which the leaf-trace has no adaxial metaxylem). x 40. (From K.2in, University 
College, London.) 
Fig. 6. An a stem preparing for leaf-production. Separating parenchymatous cells are present 
immediately in front of the single protoxylem of the leaf-trace (cf. Fig. 5). x 40. (From K20/£, 
University College, London.) 
Fig. 7. A later stage of the 13 stem and leaf-trace shown in Fig. 3 ; both stem and petiole 
possess a small stele, and wide cortex, x 27. (From K 21 e, University College, London.) 
