74 - 
hyaline cells), a condition of things spoken of by Warnstorf in his 
descriptions as a strong broadening of the border downward. 
In the perichaetial leaves the difference is carried still further, as 
in Inophloea the characteristic suppression of hyaline cells in favor of 
uniform long, narrow cells alone is confined to the basal and middle 
portion of the leaf, a generally broad lateral and apical region being 
formed of the normal network of chlorophyll-cells alternating with 
fibrillose hyaline ones ; in Litophloea on the other hand, if there be any 
such formation of a tissue of uniform narrow cells, it is in the basal, 
lateral, and apical region of the leaf, and may even occupy the whole; 
if it leave a portion with the normal network of al-ternating chloro- 
phyll and hyaline cells, it is always the upper middle portion and the 
hyaline cells are here usually, but not in all species, without fibrils. 
In proposing these two divisions as “groups,” Russow evidently 
intended to express no opinion as to the relative rank of this category, 
except that it was of less than generic value, and Warnstorf retains 
his names as series Reihen' calling Russow’s “subgroups” in this 
publication “sections.” As the Vienna rules prescribe the ranking 
order: genus, subgenus, section, subsection (series, subseries), species, 
I am, I take it, making no essential change in designating Russow’s 
groups as “subgenera.’’ The names, as neuter plurals of adjective 
forms, do not agree with the recommendations of the Vienna Congress 
for subgeneric names, but can perhaps be regarded as substantivised 
feminine singulars. No species has been discovered showing inter- 
grading forms, and the two lines are in every way so distinct that I 
have no doubt they may ultimately be recognized as separate genera. 
Russow’s “subgroups” were in no sense original with him, but 
represent simply a step in a long series of attempts to ‘ ‘arrange’ ’ the 
European species of Sphagnum. As a working-grouping of the Euro- 
pean forms their value is beyond question and they are used with 
little change by Warnstorf. That they were not, however, final, is 
best shown by Warnstorf’s not over successful attempt to apply 
them to the exotic species,^ Of the ten groups recognised in this 
work Sericea and Mucronata are, it seems to me, ill founded ; the 
western North American 5. mendodnum so unites Cuspidata and Subse- 
cunda that their seoaration becomes arbitrary ; the Central American 
5. platydadum, which clearly belongs with the Acutifolia, is placed with 
the Truncata, a group previously represented by the arctic 5. Aong- 
stromii alone, with which species it is far from being closely related ; 
and another member of the Acutifolia, the South American 5. grad- 
lescens is included among the Subsecunda. Warnstorf’s mistakes 
only serve to illustrate how tentative the European grouping neces- 
sarily was, how closely related to each other most of these groups 
are, especially when their exotic species are included with them, and 
2. Kryptogamenflora der Mark Brandenburg I. 1, p. 318 fF. 1903. 
3. Engler und Prantl, Die natuerlichen Pflanzenfamilien I. 3, I, p. 251 fF. 1900. 
