Kershaw.—A Fossil Solenostelic Fern. 
689 
the various sections. A bulging of the xylem on the outer side of the ring 
is seen, which causes the phloem, pericycle, and endodermis to project out¬ 
wards considerably. As this excrescence of the xylem grows it gradually 
becomes separated from the main mass of xylem (Fig. 7), the endodermis of 
each side of the rootlet bundle joins up, forming a complete ring, and so the 
rootlet becomes free from the solenostele. 
A solenostelic fern very similar to but rather smaller than the one just 
described appears among the Japanese preparations in Dr. Stopes's posses¬ 
sion, but unfortunately in only one slide of a series. The tissues of this stem 
agree very closely with those of Solenostelopteris japonica. As there is 
no gap in the solenostele, the section must have been taken through the 
internode of the rhizome. The xylem ring is composed of an irregular row 
of scalariform elements with scattered groups of smaller elements towards 
the outside in some parts. On each side of the xylem ring there is a well- 
marked layer of parenchymatous cells separating the xylem from the ring of 
phloem, which is made up of several layers of small sieve-tubes. The 
pericycle and endodermis can be seen on either side of the solenostele, the 
endodermis showing the same black, carbonized contents as were described 
in S. japonica. At one point a rootlet is seen arising from the stele in the 
manner described above. It seems probable, from a close comparison of the 
tissues, that this fern is merely a fragment of a smaller branch of the fern 
rhizome described. 
Diagnosis. 
Solenostelopteris , gen. nov. 
Rhizomes of fossil ferns, vascular system a solenostele. 
S. japonica, sp. nov. 
Rhizome dorsiventral, solenostele i-8 mm. diameter (without cortex). 
Xylem elements scalariform, with one series of pits on each wall. Proto- 
xylem exarch, scalariform. Internal and external phloem. Pericycle and 
endodermis well marked. Central ground tissue sclerized, with a layer 
of thin-walled cells separating it from the stele. Cortex with sclerized 
layer a short distance outside the stele, followed by thin-walled paren¬ 
chymatous cells, probably with air spaces between; the outermost cortex 
consisting of hexagonal parenchymatous cells without intercellular spaces. 
Xylem of free margin of leaf-gap considerably thicker than the rest of the 
xylem ring, lateral branch given off on same side of stele as, and in connexion 
with, the leaf-trace. 
Horizon. Upper Cretaceous. 
Locality. Hokkaido, Northern Japan. Collected by Dr. M. C. Stopes. 
Type. Stopes’s Collection, Nos. I YA. 16-24. 
