Review 
105 
to considerations of space. One would have liked to know what British 
species are referable to the genera Polyblastropsis, Blastodesmia, Phseo- 
graphina and Pilocarpon, the position of Bilimbia, why Acrocordia is 
merged in Arthopyrenia; in fact, a more detailed account of Miss Smith’s 
personal views would have been very acceptable. Her caution in regard 
to some parts of Zahlbruckner’s classification can easily be understood; 
still, the grouping of the lichens with many-spored asci in Acarosporacese 
seems justifiable, and the separation of Xanthoria from the Physcia 
group is supported by the differences in the septation and colour of the 
spores, of which the importance in classification has scarcely been 
sufficiently appreciated by our older British lichenologists except Mudd. 
With regard to Zahlbruckner’s lumping together of a number of genera 
into Lecideacese and Lecanoraceae one may be heterodox and less in 
agreement. Too much importance may be assigned to the systematic 
value of “the distinction between lecideine and lecanorine apothecia,” 
insisted upon on p. 183. Lecanoraceae may be polyphyletic from lecideoid 
ancestors and an extension of the principle which includes Blastenia with 
Placodium and Buellia with Rinodina seems justifiable. Candelaria and 
Candelariella, despite the absence of parietin, appear to have more 
affinity with Xanthoria and Placodium than with the groups under 
which they are placed. 
In a few instances one is not prepared to accept Miss Smith’s con¬ 
clusions, as for example, in the general summing-up of the evidence 
given in the case of pycnidia versus spermogonia, where the former is 
favoured. The evidence, however, on both sides is given impartially and 
the reader may use his own judgment. The evidence of Stahl, Darbishire, 
and others, as to contact between the spermatium and trichogyne, is 
not challenged. The author’s chief point against the spermatium being 
a gamete rests on its power of germination. The possibility of a gamete 
settling down to produce a new plant is familiar to algologists, and there 
does not appear to be any inherent improbability in the reappearance of 
such an ancestral character, when the spermatium is cultivated. The 
differences between the colourless, polarilocular spores of Xanthoria, and 
the brown, one-septate spores of Physcia, appear greater than is sug¬ 
gested on p. 188. According to the text, the median septum arises as 
an ingrowth from the sides of the cell. In Xanthoria the ingrowths do 
not completely meet, so that a canal is left between the two polar 
chambers. In Physcia the ingrowths meet and two distinct chambers 
are formed. The illustrations (Fig. 107) show a median septum crossing 
not only the central canal, but also traversing the ingrowth from the 
sides of the cells, so that the median septum of Physcia traverses what 
is considered to correspond to a median septum in Xanthoria. The 
Xanthoria family with Teloschistes, Xanthoria, Placodium, Callopisma 
and Blastenia , seems to be a distinct family from that of Physcia with 
the more or less corresponding genera of A naptychia, Physcia, Dimelcena, 
Rinodina and Buellia. The references to similar cell-division in Algae 
would have been better if Sphaeroplea had been mentioned instead of 
Cladophora; in the latter the wall is completed, whereas in Sphaeroplea, 
an open central pore is sometimes left. In some Siphonales ( e.g . Calli- 
psygma) an open pore is left; in Codium the stopper is incomplete when 
young and complete at an older stage. 
There are few inaccuracies or inconsistencies in the text, and for 
some of these the author is not responsible, as she is quoting the views 
or work of others. Some accident causes Collema nigrescens to have a 
distinct cellular cortex on p. 161. According to p. 371 “lichens alone are 
able to live on bare rock,” whilst it is stated on p. 394 that “in tropical 
countries the first vegetation to settle on bare rocks would seem to be 
blue-green gelatinous algae.” On p. 374 Collemopsidium is said to be 
