Evans: TAXONOMIC STUDY OF DUMORTIERA 181 
these features (according to the evidence at hand) are too incon- 
stant to be considered of specific value. In D. calcicola, as already 
pointed out, the characters drawn from the size of the thallus and 
from the sympodia developed by the sexual plants are of little 
significance. The characters drawn from the immature female 
receptacles with unfertilized archegonia and from the male re- 
ceptacles are likewise of doubtful value. Unfortunately the 
papilliform cells of the thallus are rather scantily developed in 
the type material, but this condition is often pupien ey in un- 
doubted D. nepalensis. 
For valuable assistance in the preparation of this paper the 
writer would express his thanks to Professor W. G. Farlow, 
Professor D. H. Campbell, Dr. Marshall A. Howe and Miss 
Caroline C. Haynes. Through their generosity it has been pos- 
sible to study the types of D. irrigua, D. nepalensis, D. tricho- 
cephala, D. dilatata and D. calcicola, as well as other. interesting 
and authentic material. 
SHEFFIELD SCIENTIFIC SCHOOL, 
ALE UNIVERSITY. 
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5. Goebel, K. Wasserpflanzen. Pflanzenbiologische Schilderungen 
2: 217-386. pl. 26-31 +f. 63-121. Marburg. 1893. 

2. 

6. Organographie der Pflanzen. 2d ed. 2. Bryophytes. 
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