1917] Butters,— Studies in Ferns — Athyrium 181 
bent sharply back upon itself, with the two sides in contact, so that 
it stands in the midst of the sporangia of the distal half of the sorus. 
The indusia are usually provided with an abundance of long multi- 
cellular cilia. These are occasionally rather few in number, and in 
old sori they often become so shrivelled that they are not easily seen, 
except with the compound microscope, and after careful dissection. 
In no specimen examined were they wanting. The average height of 
the indusia, not including the cilia, is 0.55 mm., and their average 
length in the larger sori is 0.8 mm.! In the case of the short asplenioid 
sori near the tips of the pinnules the indusium is often higher than it is 
long. At both extremities the indusium ends abruptly, so that its 
sides meet the line of attachment nearly perpendicularly, and some- 
times it is even contracted towards the base.” 
The stalks of the sporangia are short and very frequently proliferate, 
the branch usually bearing a secondary sporangium. Occasionally 
the secondary sporangium is abortive, and rarely it is replaced -by a 
glandular structure. In no specimen seen are such glands freely and 
uniformly produced as they are in nearly all east American material. 
The spores are yellowish, sparsely papillate, and average 39.1 X 
24.1 win size. 
3. Tue Lapy FERNS oF THE EASTERN UNITED STATES AND CANADA. 
In the eastern parts of North America there are two species of the 
lady fern group which appear to be amply distinct from each other 
and from the true Athyrium Filix-femina. These are A. asplenioides 
(Michx.) Desv. and A. angustum (Willd.) Presl. The former is a 
southern species, ranging from Florida to Texas, and north to Mis- 
souri, Indiana, Ohio, and along the Atlantic coast to eastern Massa- 
1 All measurements of indusia in this paper were made upon indusia dissected off from the 
frond and flattened out under a cover glass. The length is always measured in a straight line, 
as nearly as possible parallel to the line of attachment of the indusium, the height in a straight 
line from the attached edge of the indusium to its free margin. See text-figure 3, p. 175, and 
text-figure 5, p. 176. 
2 The soral characters of the true A. Filix-femina are reflected in the treatment of it by Euro- 
pean botanists. Thus Linnaeus, who defined Polypodium, “ Fructificationes distributae in 
puncta rotunda, per paginam folii aversam (Gen. Pl. ed. 5, 485, 1754), placed the lady fern 
in that genus between P. cristalum and P. Filiz-mas, and P. aculeatum, P. rhaeticum (a mixture 
of Athyrium Filix-femina and A. alpestre) and P. noveboracense. It has been placed in Nephro- 
dium and Aspidium and by most recent European botanists in Athyrium. Those who, like 
Mettenius and Hooker placed it in Asplenium have held very broad views of the extent and 
characteristics of the latter genus. 
