386 MR. G. S. WEST ON 
The variations in the relative proportions of this species are 
illustrated by the preceding diagram (p. 385), which is con- 
structed to show the independent variation in different directions 
of the length, breadth, and isthmus. The specimens are taken 
purposely from widely separated localities. 
7. XANTHIDIUM SMITHI, Arch., var. VARIABILE, Nordst., 
^ Algol. Smäsak.,” Bot. Notiser, 1887, p. 159; Kongl. Sv. Vet.- 
Akad. Handl. Bd. xxii. no. 8, 1888, p. 44, t. 4. ff. 27-29.—I 
have seen this plant in many parts of the British Isles, some- 
times in large quantity, and at other times very sparingly, but 
in all cases in Sphagnum-bogs. From the constant manner in 
which it retains its distinctive features, I am much inclined to 
regard it as a separate species apart from X. Smithii, Arch. 
The semieells are usually pyramidate, with broadly truncate 
apices, but many forms are met with intermediate between such 
a trapezoid and a rectangular semicell. There are three spines 
at each of the basal angles, these showing most distinctly at each 
of the poles of the vertical view. The latter are deseribed 
and figured by Nordstedt (l. c.) as truncate, but I always find 
them to be rounded, and this has elsewhere been mentioned to 
be the case (cfr. Journ. Roy. Mier. Soc. 1896, p.156). Three 
spines are generally present at each of the superior angles of 
the semicells, although two or even four are not uncommonly 
observed, and their disposition is often somewhat irregular 
(ofr. Pl. 8. figs. 20-22, b, b' of vertical views). The central pro- 
tuberance in the great majority of specimens is in the form of a 
simple papilla, but in a few I have observed it to be truncate and 
trituberculate (Pl. 8. figs. 20, a & b). 
8. COSMARIUM Lave, Rabenh., Flor. Europ. Algar. iii. 1868, 
p. 161.—This species, first figured by Nordstedt in Ofvers. af K. 
Vet.-Akad. Fórh. 1876, no. 6, t. 12. f. 4, is subject to consider- 
able variation in the form of the semicelis. Those of the typical 
form are of a somewhat semielliptical or subsemicircular outline, 
and very slightly retuse in the middle of the apex, the latter 
feature being characteristie of all forms of the species. A pure 
gathering obtained from the North of France consisted of very 
fine, large forms, mostly typical in outline (Pl. 10. figs. 1 & 2), 
but in some cases with a tendency of the semicells to become 
more rounded: long. 28-34, ; lat. 19-23 u; lat. isthm, 5-5-8 [a 
