456 Chronicles of Science. [July, 
American ‘Journal of Science and Arts, M. Leo Lesquereux makes 
some important remarks in regard to fossil ferns. He says that the 
family of ferns was represented at the coal epoch by species which 
are easily referred to a very few typical forms. If we consider the 
figure of the leaves, 7.e. their contour and venation, the only part 
generally preserved in the shales of the coal measure, all the species 
may be comprised in the three sections —Neuropteridee, Pecopteridee, 
and Sphenopteridee. From the scarcity of fructified specimens of 
fossil ferns in the coal measures, it might be supposed that most of the 
species were without fruit. The want of fructification is rather casual 
than real. By careful examination at some places, where the remains of 
a species are found in abundance, one may generally succeed in finding 
traces of fructification. 'The sporangia seem in most cases to have dis- 
appeared, from long and continued immersion in water. Moreover, the 
fern fronds have usually the lower surface attached to the shale in 
such a way that the fructification cannot be observed. We can some- 
times observe an indistinct outline of the form of the sporangia 
printed in relief through the carbonized tissue of the fronds. The 
scarcity of large stems would seem to lead to the conclusion that 
during the formation of coal, tree-ferns were of rare occurrence, at 
least when compared with the great number of ferns. If we consider 
as remains of true arborescent ferns, only those whose outer surface 
is marked by large oval cicatrices, and known under the names of 
Caulopteris and Protopteris, it is certain that they are very scarce in the 
coal measures both of Europe and of America. In his genera, Unger 
counts in the Protopteridee of the coal, ten species only, distributed in 
five genera; and of these species, five are considered by Brongniart 
and Lindley as belonging to Sigillaria or Lepidodendron. Brongniart 
enumerates only six species of Caulopteris ; Geinitz gives four, three 
of them published by Brongniart as Sigillaria, and one by Artis as 
Megaphytum ; and Goeppert, in his ‘ Fossil Flora des Uebergangsge- 
birges, has none. Some have supposed the genus Psaronius to be 
allied to Protopteris, and if so, the numbers of tree ferns would be 
much increased. Brongniart, however, looks upon Psaronius as 
allied to Lepidodendron. The cicatrices of Caulopteridee are geue- 
rally distant, placed on the stems in the spiral order 2. When ina 
good state of preservation they are generally oval, or obovate, and 
elongated at both ends by a somewhat deep furrow. They have in the 
middle the mark of a simple bundle of vessels, in the form of a horse- 
shoe, and the central scar is surrounded by an oval annulus. The 
genus Megaphytum, according to Brongniart, ought to be united with 
the genera Bothrodendron or Ulodendron, and referred to Lepidodendron, 
as representing merely a modification of the last genus. Lesquereux, 
on the contrary, considers Megaphyiwm as a tree fern, and he is led to 
this conclusion from an examination of the cicatrices of Megaphytum 
protuberans. 
Messrs. Cloez and Gratiolet find that the gas exhaled fron: aquatic 
plants exposed to the light in ordinary water slightly impregnated 
with carbonic acid contains besides oxygen a notable quantity of 
nitrogen. The latter gas they consider as proceeding from the decom- 
