690 
Kershaw,—A Fossil Solenostelic Fern. 
Affinities. 
From the small fragment of the stem available and without any indica¬ 
tion of what the external characters were, it is impossible to determine the 
definite affinities of the fern. The vascular anatomy is the only ground to 
work from, and the exact value of that as a factor in classification of ferns is 
yet hardly known ; moreover, there is much necessary information concern¬ 
ing the vascular anatomy lacking, for the structure of the petiole and its con¬ 
nexion with the stem are not known. Many of the anatomical features 
resemble those in the more typical solenostelic forms of the Davallieae, 
in particular Microlepia. The marginal thickening of the xylem of the leaf- 
gap, which seems a point of considerable interest and importance, is developed 
to a similar extent in Microlepia hirta. The distribution of sclerenchyma, 
arrangement of xylem and phloem, &c., are also very similar in this species. 
Owing to our ignorance of the soral and sporangial characters, and the 
incompleteness of this, the only specimen of the plant, this account of 
Solenostelopteris japo 7 iica is necessarily a purely descriptive one. The 
specimen is interesting as affording an example of a definite stelar type 
common in recent ferns, but not previously described in detail among 
fossils. It also adds a new type to the Cretaceous Flora, as described by 
Stopes and Fujii. 1 We may perhaps venture to go so far as to recognize it 
as probable that the affinities of the fossil are with the typical solenostelic 
members of the Davallieae. 
I wish to express my sincere thanks to Dr. Marie Stopes for so kindly 
placing her material at my disposal, and also for the helpful interest she has 
shown. To Dr. Lang, also, I am indebted for many useful suggestions. 
DESCRIPTION OF PLATE LVIII. 
Illustrating Miss Kershaw’s paper on a Fossil Solenostelic Fern. 
Fig. 1. Photograph of the solenostele below the leaf-gap, showing at a on the dorsal side of the 
stele the greater thickness of the xylem. c. scl., central sclerized ground tissue ; s., thin-walled cells 
amongst sclerized ones; x., xylem. (Slide I YA 17.) 
Fig. 2. Drawing of a small part of the solenostele, showing details of anatomy. 0. per., i. per., 
outer and inner pericycle ; 0. end., i. end., outer and inner endodermis; 0. ph. } i. ph., outer and inner 
phloem ; p.x ., protoxylem ; par., parenchymatous cells. (Slide I YA 16.) 
1 Stopes and Fujii (’10), Studies on the Structure and Affinities of Cretaceous Plants. Phil. 
Trans. Roy. Soc., London, Series B, vol. cci. 
