160 
F. Cavers. 
Fam. 8. jfubuloideae. In Frullania dilatata, gemmae are some¬ 
times formed on the margins of the leaves, each consisting of four 
to six cells as a rule and being discoid or irregular in form. The 
outer surface of the perianth in this species hears numerous 
irregular outgrowths, each made up from two to five or six cells. 
1 hese outgrowths may he regarded as gemmae, for the writer has 
found that when the whole or a portion of a perianth is isolated 
and kept under cultivation, some of them give rise to leafy shoots, 
either before or after becoming detached from the perianth. The 
caducous lobules of F. fragilifolia have already been described 
under the heading of adventive shoots, but these organs might 
reasonably be regarded as gemmae, since they become detached 
from the plant before giving rise to the new leafy shoot. In several of 
the Lejeuneae, there are produced discoid gemmae, similar to those 
of Radula in general form, but in some cases showing peculiar 
features. In 7'hallolejeunen (Metzgeriopsis) pusilla, a remarkable 
form discovered in Java by Goebel, 1 the vegetative portion of the 
plant consists of a repeatedly-branched thallus with toothed 
margins, whilst the sexual organs are borne on short leafy shoots 
each arising from the apex of a branch. The thallus bears on its 
upper surface and its margins numerous discoid gemmae, each 
consisting of an oval plate of cells, lying parallel with the surface 
of the thallus, to which it is attached by a short stalk-cell. The 
mature gemma consists of about twenty cells, arranged in a single 
layer, and shows two growing-points occupying opposite sides of the 
gemma and each showing a wedge-shaped apical cell. Similar 
gemmae are also found on the male and female bracts. 
Discoid gemmae are formed on the leaves of Cololejeiinea 
calcaren (Fig. 8), C. minutissima , C. microscopca, Eulejeunea serpylli- 
folia , and Colurolejeunea calyptrifolia , all of which occur in Britain. 
In some tropical forms described by Goebel, e.g., Cololejeiinea 
Goebclii, Odontolejeunea inirabilis, the gemmae have two growing- 
points, as in Metzgeriopsis , and some of the marginal cells are 
modified to form organs of attachment. The writer has followed 
the development of the gemmae in Cololejeunea calcaren (Fig. 8), 
which are sometimes found in abundance on the lower surfaces of 
the leaves, each consisting when mature of a circular or oval disc, 
one cell in thickness, attached to the leaf by a single stalk-cell 
which is inserted at the centre of the lower surface of the gemma. 
o 
1 boc. cit., p. 54, Tab. 6—8 ; also Scliiffner, V., Morphologie mid 
systematisclie Stellung von Metzgeriopsis pusilla. Oesterr. 
botan. Zeitsclil ift, 1893, p. 4 of reprint. 
