682 Marsh —The Anatomy of some Xerophilous Species of 
Sinnott’s corollaries to his general proposition. Especially should this be 
remembered before adopting Sinnott’s sceptical attitude towards the theory 
of Tansley and Gwynne-Vaughan, ‘who consider the siphonostele to have 
been produced by the influence of an arched trace on a protostele 
That the two theories are not so incompatible has been recently 
established by Salisbury (6), who has shown that narrowing of the base 
of the leaf-trace, found so frequently in Ferns, has no appreciable influence 
in checking the free supply of water to the leaf. The transpiration current 
being practically as great as if there were no basal narrowing of the petiolar 
stele, the effect of the leaf-trace on the conducting tissues of the stem, which 
supply the water necessary for this transpiration current, will be the effect 
of the full current in the main part of the petiole. 
Spore Counts. 
All the species except Cheilanthes persica were bearing ripe sporangia, 
and counts were made of the spores per sporangium, the results being as 
follows : 
Pcllaea androniedaefolia 30, 31. 
P. falcata 60, 56. 
Cheilanthes Fendleri 53, 57. 
Ch. gracillima 30, 3 1 . 
Ch . lanuginosa 32, 30. 
The results show that the purely solenostelic form has in each genus more 
spores per sporangium than the dictyostelic species. Among the Cheilanthes 
Ch. Fendleri has the larger number, and this corroborates the evidence for 
the primitiveness of this species derived from the anatomy of the stem and 
petiole. 
Summary. 
1. The xerophilous species of Pellaea and Cheilanthes show well- 
marked leaf adaptations. Hairs or scales on the lower surface, inrolled 
margins, thick cuticle, and palisade parenchyma are the chief characters 
observed. 
2. The Cheilanthes species, all belonging to § Physapteris , show a wide 
range of stelar anatomy in their stems. Ch. Fendleri has a simple soleno- 
stele. Ch. gracillima has a solenostele becoming occasionally dictyostelic 
by the interpolation of an extra leaf, and Ch. lanuginosa , bearing its leaves 
much more closely on the stem, only rarely shows a complete ring in cross- 
section. These three have dorsi ventral rhizomes, while Ch. persica has 
a radial dictyostele which is much more dissected than that of any of the 
three other species. 
3. Of the genus Pellaea , P. androniedaefolia was the only xerophytic 
