28 AMERICAN FERN JOURNAL 
cludes seventy-two species. These articles would ap- 
pear to be admirably designed to serve the purpose for 
which they were intended, namely, to interest and in- 
form teachers of nature study and elementary science. 
Beginners in fernstudy will find them helpful and interest- 
ing. The only point that might be commented upon 
as a lack was the absence of any mention of fern books 
for further information—such books, for instance, as 
Clute’s ‘‘Our ferns in their haunts,’’ Parson’s ‘‘ How to 
know the Ferns,’ Slosson’s ‘‘How Ferns grow’, and 
Waters’s ‘‘ Ferns.”’ 
Two separates from Carl Christensen were received 
in October, both issued in 1920. 
“New species of Hymenophyllaceae from Madagas- 
car” was published as Fascicule 12 in Notes Ptérido- 
logiques of Prince Roland Bonaparte. Five new species 
of Trichomanes are described, together with related 
species of the African islands. 
‘A monograph of the genus Dryopteris, Part II; The 
tropical American bipinnate-decompound species.’ Mém. 
de 1’Acad. Roy. des Sci. et des Let. de Danemark, Cop- 
enhague; Sect. de Sci. Ser. 8; 6: 1-132; f. 1-29. 9 
Je 1920 
Part one of Christensen’s Dryopteris monograph, re- 
viewed at the time of its appearance, 1913, dealt with 
the species of Dryopteris less than twice pinnate. In 
the present paper, all the remaining tropical American 
species are described, making a total of 347 species. 
Mention is made of the fact that 17 other species occur 
north of the tropics, a grand total of known forms of 
364. Mr. Christensen estimates 500 as the probable 
number of American species with a probable equal 
number native in the Old World. When one pauses to 
consider a genus of one thousand species, of which less 
than a score are common in the United States, the diffi- 
culty of reaching well grounded conclusions from a 
