Anatomy of So lenoste lie Ferns : /. L ox soma . 97 
elements are found towards the external periphery. Russow 
also comments upon the absence, or at any rate the extreme 
rarity of spiral or annular elements in the stem. These 
features are quoted with the intention of pointing out the 
general anatomical similarity of Marsilea to a simple plan 
of Fern-anatomy, but without drawing the comparison defi- 
nitely with any individual genus or order. 
I take this opportunity to express my gratitude to Professor 
Bower for the interest he has taken in my work, and for the 
valuable advice and assistance he has given me in the con- 
struction of this paper. 
I have also to thank Dr. W. H. Lang for useful advice 
upon many points. 
EXPLANATION OF THE FIGURES IN PLATE III, 
Illustrating Mr. Gwynne- Vaughan’s paper on Loxsoma. 
Figs. 1, 2, 3, 6, 8, and 9, are from photographs ; a more or less under-exposed 
print was taken, and this was accentuated with a pencil ; Figs. 5, 10, 1 1, and 12, 
are camera lucida diagrams ; Figs. 4 and 7 are diagrams. The following lettering 
is used throughout: e, external endodermis ; e' , internal endodermis ; P, external 
pericycle ; P f , internal pericycle ; ph , external phloem ; ph' , internal phloem ; 
pph, external protophloem ; pph! , internal protophloem ; x, xylem ; prx, proto - 
xylem. 
Fig. i. Portion of a transverse section of an internode of the rhizome: ss, 
solenostele ; at the zones marked ( x ) the ground-tissue is more sclerotic than 
elsewhere. The solenostele is preparing to give off a leaf-trace on the left, x 12. 
Fig. 2. Portion of a transverse section of the solenostele : a, o', zones of paren- 
chyma intervening between the two endodermal layers (e, e r ) and the sclerenchyma 
of the ground- tissue, x 150. 
Fig. 3. Portion of a transverse section of the solenostele towards the apical 
region of the stem. The xylem is not yet completely differentiated, although the 
protoxylem elements {prx) are already well thickened and lignified : m, un- 
thickened elements of the metaxylem. x 100. 
Fig. 4. Diagram showing the form of the vascular system at the nodes of the 
rhizome : ss, solenostele ; It, deparitng leaf-trace ; Ig, leaf-gap. The arrow points 
towards the apex of the rhizome. 
Fig. 5. Transverse section of the petiolar meristele at a point below the middle 
of the petiole ; slightly diagrammatic : hk, the hooked ends of the xylem-strand ; 
H 
