sorus opens toward the margin of the frond. In Monogramma and Vit- 
taria (fig. 22), the sori are in deep slits, the effect being as in Asplenium 
Phyllitidis, but the protection of the more open slits is perfected by capi- 
tate paraphyses. In Polypodium incurvatum, and more prominently in 
P. subauriculatum, P. nigrescens , P. Bchneideri and P. papillosum , the 
sori are “immersed” for several times the thickness of the frond, forming 
very prominent projections from the upper 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 there are a considerable number of ways in which they are 
adapted to perform this latter function well. In other 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 Nephrodia and in many of their relatives, the indusia 
partly or completely disappear as the sporangia mature. The segments 
of Poly podium cucullatum and P. gracillimum flatten out, as do,- in 
varying measure, the reflexed margins of the Pteridece. The indusia of 
the Aspleniece curl or bend outward to permit the drying and scattering 
of the spores. In Asplenium scandens, and without doubt in many other 
species, the indusia ar.e motile, bending outward 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 Nephrodium procurrens , N, aridum , N. cucullatum (few) , 
N. 1677, N. Bordenii, (decidedly hispid), Microlepia strigosa (long basal 
hairs), and Adiantum diaphanum ; and glandular-hairy or glandular- 
ciliate in Nephrodium 1712, N. setigerum (with fugacious indusia), 
N. 1685, Aspidium angulatum (fig. 23), and Oleandra colubrina nitida. 
It has already been stated that paraphyses are in general water-repellant 
structures, in adaptation to which function they are provided with oily 
heads. Among the San Ramon ferns provided with these are Aspidium 
leuzeanum, Oleandra neriiformis , Microlepia pmnata, Dennstaedtia Wil- 
liamsi, Vittaria, Anthrophyum, Taenitis, Hymenolepts, Polypodium 
■Subauriculatum, Lomagr am, ma, Achrostichum and Cheiropleuria. The 
paraphyses are in part a substitute for indusia and often occur on ferns 
such as the Achrostichece, which could not have indusia; but they are 
not rarely present in indnsiate sori. They are notably developed on 
Lomagramma and Achrostichum (fig. 24), the brown color of the fruiting 
surface of the latter 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 Nephrodium, such as N. setigerum (glandular), 
N. diversilobum (fig. 25), but not in N. canescens, and Meniscium. 
