310 
THE JOURNAL OF BOTANY 
A KEY TO THE BRITISH SPHAGNA. 
By W. R. Sherrin, A.L.S. 
The following key to the species of Sphagnum is complementary 
to Wheldon’s Synopsis of the European Sphagna (1917), in which 
the varieties and forms are fully dealt with. For a complete descrip¬ 
tion of the species the student is referred to Warnstorf’s Sphagnologia 
Universalis (1911). The beginner will find Dixon’s Handbook of 
British Mosses of great help in taking up the family ; the limited 
number of species described by him correspond more or less accu¬ 
rately with the leading or titular species of the groups in the follow¬ 
ing list:—- 
General Key to the Groups. 
A. Branch leaves at the apex truncate and 
toothed. 
I. Chlorophyllose cells exposed on the upper 
(inner) or lower (outer) surfaces or on 
both. 
a. Chlor. cells of br. Is. in section trian¬ 
gular or trapezoid. 
Chlor. cells with the base of the 
triangle on the upper surface... Group Acutifolia. 
Chlor. cells with the base of the 
triangle on the lower surface. 
Stem cortex reddish; br. Is. squar- 
rose, spreading . Group Squarrosa. 
Stem cortex pale yellowish; hr. 
Is. mostly undulate . Group Cuspidata. 
b. Chlor. cells of hr. Is. barrel-shaped to 
rectangular, exposed on both sur¬ 
faces . Group Sub secundum. 
II. Chlor. cells completely enclosed. Group Rigida. 
B. Br. Is. at apex cucullate (hooded) . Group Cymbifolia. 
Group Acutifolia. 
A. Most of the cortical cells of the stem with 
large non-bordered pores. 
I. Stem Is. spatulate, fimbriate on the 
rounded apex and on the lateral margins 
above. S. f mbriatum Wils. 
II. St. Is. Ungulate, fimbriate at the apex only. 
a. Wood cylinder of the st. never red; 
st. cortex with large pores . S. Girgensohnii Russ. 
b. Wood cylinder red; st. cortex with 
smaller pores. S . Bussoivii Warnst. 
B. Cortical cells of the st. rarely with small 
scattered pores. 
1. St. Is. with narrow base; br. Is. dentate... S. nolle Sull. 
