6yS Marsh . — The Anatomy of some Xerophilous Species of 
There was, however, in all five species, just as great a development of 
phloem and endodermis on the inside of the stele as on the outside, 
contrasting in this respect with the reduced types of stele described by 
Jeffrey ( 5 ) in some species of Antrophyum and Vittaria. But at the leaf- 
gap the phloem was found to be absent in every case, so that there was no 
continuity of internal and external phloem (Fig. 7). In fact, in the gap 
xylem and endodermis are constantly separated by only two or three layers 
of parenchyma. Even Pellaea falcata shows reduction of the phloem in 
the leaf- gap, though its stele has no other reduced characters. 
Petioles. 
The anatomy of the petiole was carefully investigated in each species. 
The petiolar stele forms a single strand in every case, lying surrounded by 
a sclerenchymatous cortex, which can be fairly easily separated, leaving 
Fig. 9. Portion of transverse sec- 
tion of Pellaea andromedaefolia. i.ph. — 
internal phloem ; e.ph . = external phloem ; 
tr. = tracheide ; par. — parenchyma. 
P* 
Fig. 10. Transverse section of xylem of stele 
of Cheilanthes Fendleri petiole, px. — proto- 
xylem. 
only the central trace. The stelar strand thus obtained was embedded 
and microtomed. By cutting at 10 /x and keeping every tenth section, 
I obtained a series of sections at 100 /x intervals, from the base upwards. 
At the very base in each species there is a simple adaxially curved anarch 
leaf-trace, but the changes in structure found on following the petiolar 
strand upwards vary considerably, so that for each species it is best to 
have a separate description. Diagrams of the various stages are given 
in Fig. 11. 
Cheilanthes Fendleri . The anarch C-shaped strand soon develops 
three protoxylems, all of which are endarch. The metaxylem immediately 
exterior to the median protoxylem dies out at a higher level, but the two 
portions of the stele thus left separate (except for the median protoxylem 
connexion) soon rejoin. This junction, however, is effected in such a way 
that our protoxylem is now in an exarch position. This protoxylem next 
