rock. The perpendicular ledges thus exposed are much of the day in the 
shade, and wherever water trickles from above they become covered with an 
interesting and uniform moss vegetation, the species mentioned being the 
most characteristic. Another companion forming extensive dense mats and 
fruiting abundantly, is Gymnostomum curvirostre , but this and the Brymn 
seem able to stand a somewhat drier situation, for depauperate forms of both 
occur also higher up on the bluffs. 
In striking contrast with this river level flora is that at the top of the 
bluffs, only four hundred feet higher. The most abundant and most charac- 
teristic moss here is Grimmia teretinervis , covering the calcareous sun- 
burnt sand rock, exposed to an all day sun, in black flat cushions, which are 
hardly recognized as plants by young students. This species is always ster- 
ile. On the same level occur also, with the same regularity, only less abun- 
dantly, Coscinodon Raui and C. Wrightii, both fruiting. Their principal 
companions are Tortula ruralis , Tortella fragilis and Ditrichum fiexi- 
caule brevifolutm . all sterile. 
We have thus on a small scale a real arid region moss flora at the tops of 
our Mississippi bluffs enjoying essentially the conditions prevailing in dry 
countrjes. While at the base, near the river level, there thrives another uni- 
form flora characteristic of better watered regions. And the interesting 
part is the fact that this narrow strip in altitude extends for fully a hundred 
miles or more along our Great River. 
This peculiar parallelism is made possible by the geological formation, 
the several alternating strata of Lower Silurian lime and sand rock lie, in the 
Upper Mississippi Basin nearly as horizontal as when they were laid down 
millions of years ago, so that the Great River with its tributaries large and 
small, has made its valley by erosion through these strata establishing iden- 
tical conditions at the two levels referred to. Winona, Minn. 
DIE EUROPAEISCHEN LAUBMOOSE. 
By G. Roth, Leipzig, Verlag von Wilhelm Engelmann. 
John M. Holzinger. 
This bryological work comprises two 8vo. volumes of considerable size 
and appeared in parts in rather rapid succession since early in 1904. The 
first volume comprises the Cleistocarpi and Acrocarpi to Bryaceae, and 
covers five hundred and ninety-eight pages of printed matter, exclusive of 
thirteen pages of Table of Contents, and fifty-two plates closely crowded 
with drawings of microscopic details of the species described. The second 
volume, completed in 1905, concludes the Acrocarpi and completes the Pleuro- 
carpi, covering seven hundred and thirty- three pages, accompanied by sixty- 
two plates similarly replete with figures. The descriptions are accurately 
drawn up and go into details after the fashion of Limpricht, supplementing 
in a very helpful way the short and often too incomplete descriptions of 
many older species. Great care is taken to record the substratum, mode of 
occurrence and the distribution of the species treated. The legend for the 
