50 
or erect, nor its symmetry, radial or bilateral, seems to be a very deep- 
seated or firmly fixed character, for both change in many instances within 
universally recognized generic or subgeneric limits, as in “ Goniopteris” 
and Eu-Poly podium. , The correlation between length of stem and length 
of stipe is too obvious to need any discussion; ferns with scandent or 
wide-creeping rhizomes have short stipes, while those with erect rhi- 
zomes have the tufted stipes long enough to separate the fronds. 
Meshy rhizomes serving as water-reservoirs are found in Drynaria 
and its relatives, most notably in Polypodium Jieracleum , 26 and less 
developed in Photinopteris and Polypodium affine. The rhizome and 
stipe of Scolopendrium pinnatum are fleshy, as is the stipe of Antrophyum 
latifolium. 
All rhizomes are protected against loss of water at the apex, and many 
throughout their length, by scales which vary in form, size, and texture. 
Exceedingly harsh paleae are found on Dipteris and Dennstaedtia Wil- 
liamsi, two ferns with notably stout rhizomes. It is very probable that 
these are protective against animals, such as deer and hogs which are 
very numerous, but which never, so far as I have observed, touch these 
species. Similar scales protect the fleshjr crowns of various Cyatheacece. 
The muricate stems of Stenochlaena, and muricate stipes of Dennstaedtia 
erythrorachis, Diplazium polypodioides and other species, as well as of 
Athyrium silvaticum probably have the same function. Dead bases of 
stipes must -provide other rhizomes with an unpalatable mantle, but most 
fern stems are too hard to need protection of this kind. 
Many stems contain chlorophyll when exposed to the light. It is 
regularly present in those of Polypodium accedens, P. dolichopterum, 
P. commutatum and P. Schneideri. 
Light correlations. — The correlation between length of rhizome and 
length of stipe has just been mentioned. A similar correlation exists 
between length of one or the other of these and the development of 
the lowest pinna;. Deltoid fronds — that is, fronds with elongate lowest 
pinnae — would seriously interfere with each other’s light if they were 
not borne on wide-creeping rhizomes, as is the case in Davallia and 
Humata; or on very long ascending stipes, as is true of most species 
of Aspidium, Nephr odium sparsum, N. intermedium , Dennstaedtia ery- 
throrachis, Adiantum mindanaoense, Scliizostege pachysora, Pteris excelsa 
and P. pluricaudata ; or on comparatively short, but more horizontal 
stipes, as in Leptochilus latifolius and Psomiocarpa apiifolia. Fronds 
with short stipes, unless these are very remote, usually have the pinnae 
reduced toward the base; illustrations with creeping rhizomes are Neph- 
rodium aridium, Arthropteris , Lindsay a hymenophylloides, L. Havicei , 
Polypodium celebicum, P. obliguatum, Prosaptia, Drynaria (normal 
26 Goebel : Pflanzenbiologische Schilderungen (1889), 1, 202. However, Profes- 
sor Goebel is in error when he cites the Hymenophyllacew, because they have no 
store of water, as being quickly killed by dry air. 
