57 
soms opens toward the margin of the frond. In Monogramma and YiU 
taria {f\g. 22), the sori are in deep slits, the effect being as in AspJeniam 
PhyUiiidis, but the protection of the more open ?lit.- is perfected by capi- 
tate paraphyses. In Folypodiuni incur vatum, and more 2>rominentIy in 
P. suhauriculaium, P. nigrescens, P, Schneidert and P. papillosum, the 
sori are "immersed" for several times tlio iliickness of the frond, forming 
very prominent projections from the n]>per surface. 
The structures which serve to prevent the desiccation of young sori 
serve also, without exception, to make their exposure to liquid water 
impossible and tliere arc a considerable miinber of ways in.whicli they are 
adapted to perform this latter function well. In otiier cases, structures 
at first clearly protective are done away with or changed in such a way 
as to make the mature sporangia as exposed as possible. Thus, in a 
large part of our NepJtrodia and in many of their relatives, the indnsia 
partly or completely disappear as the sporangia mature. The segments 
of Polypodium cucullatum and P. gracillimum flatten out, as do, in 
varying measure, the reflexed margins of ih&PieridcLV. The indusia of 
the Aspleniece curl or bend outward to permit the drying and scattering 
of the spores. In Aspleninm scan-dens, and without doubt in uumy otlier 
species, the indusia are motile, bending outv\ard when dry, but closely 
appressed when wet. This movement deserves careful, study, both as to 
its commonness and its mechanism. I have noticed it to exist, but in a 
less pronounced manner, in Onychium. 
The indusia are beset with hairs, which I interpret as water-repellant 
structures, in Neplirodium procurrens, N. aridum, N. cucullatum (few), 
N. 1677, N. Bordenii, (decidedly hispid), Microlepia strigosa (long basal 
hairs), and Adiantum diaplianum; and glandular-hairy or glaiidular- 
ciliate in Neplirodium 1712, N, setigerum (with fugacious indusia), 
N. 1GS5, A^pidium mgulatum (fig. 23), and Oleandra colvhrina nitida. 
It has already. been stated that paraphyses are in general water-repellant 
structures, in adaptation to which function they are provideil with oily 
heads. Among .the Sau Eamon ferns provided with these arc Aspidium 
leuzmnum, Oleandra neriiformis, Microlepia pinruita, Dennslaediia Wil- 
Uamsi, Vittaria, Anthrophyum, Taenitis, Ilymenolepis, Polypodium 
subauricnlatum , Lomagramma, Achrostichuni and Cheiropleuria, The 
paraphyses are in part a substitute for indusia and often occur on ferns 
such as the Aclirostivhew, which could not have indusia; but they are 
not rarely present in indusiate sori. They are notably developed on 
Lomagramma and Aclirosiichum (fig. 24), the brown color of the fruiting 
surface of the lalicr being due to them, while the sporangia are green. 
The branched form, like the oiliness, is evidence that they are specialized 
for protection against water rather than against desiccation. 
Hairs on the end of the sporangia have the same effect. They are found 
in a number of species of Neplirodium, ^^if^l^ as N, setigerum (glandular), 
N, dli'crsilohum (fig. 25), but not in N, cancscem, and Meniscium. 
