GENERAL MORPHOLOGY 
409 
between them, as well as the variations in the individuals in either genus, 
afford an important basis for 
comparison with other forms, 
throwing light upon fluctuations 
of structure which would other- 
wise be more puzzling than 
they now appear to be. 
Both genera are rootless. 
The green, more or less shrubby 
shoot, is established in the 
substratum, which is usually of 
humus character, by means of 
a plexus of leafless rhizomes 
invested with rhizoids, and 
penetrated by a mycorhizic 
fungus. The nutrition of these 
plants is thus of a mixed char- 
acter, partly saprophytic, partly 
by photosynthesis. The aerial 
shoots bear appendages of two 
sorts, described as foliage leaves, 
which are simple, and sporo- 
phylls, which are forked. These 
may be associated together 
irregularly on the same shoot 
which thus takes the character 
of a lax, undifferentiated stro- 
bilus. 
In Zmesipterts, of which the 
single species Z: fannensis is 
native in Australasia, though 
extending northwards to the 
Philippines, the structure is 
more simple than in Pszlotum. 
Its habit is peculiar, the plant 
being established on the trunks 
of tree-ferns, though occasion- 
ally it has also been found 
upon the ground. 
The rhizome, which fixes it in 
the substratum, is repeatedly 
branched in a_ dichotomous 
manner and is without appen- 
dages other than rhizoids. 
growing 
Fic. 226. 
Tmesipterts tannensis, Bemh. A = Habit-figure of a whole 
plant (pendent form), showing a dichotomy. Natural size. 
4S-£, sporophylls, with synangia; 8, seen from the side; CU, 
from above; J, after dehiscence ; £, from the under (dorsal) 
side, allxabout 3. A=rhizome % natural size. G=trans- 
verse section of old stem, x4. (After Pritzel in Engler and 
Prantl, Vat. P#anszenfam.) 
Branches of this system turn upwards to the 
light, and develop as the aerial shoots: 
these are usually themselves 
