Salmon. — On the Genus Fissidens . 1 13 
similar to those found on the base of the stem of most 
species. It is more probable, however, that these outermost 
floral leaves show a modified rather than a primitive form, 
and have arisen through the bud-like shape of the inflo- 
rescence. 
The second theory has no evidence to sypport it, and 
hardly requires serious consideration. Debat ( 16 ), its author, 
examined the vegetative buds of F. adiantoides , and came 
to the conclusion that in the young leaves, up to a certain 
stage, the vaginant laminae are absent (‘ a 6 centiemes de 
millimetre on a une representation exacte de ce que sera 
plus tard l’organe appendiculaire, moins la feuille normale ’). 
For this reason Debat rejects Robert Brown’s theory, and 
gives this explanation : — ‘ II nous semble que Ion pourrait 
assimiler tres exactement 1’evolution des lames foliacees 
de generations successives a celle de rameaux naissant les 
uns des autres par dichotomie. Ces rameaux seraient, a la 
verite, modifies par la production de deux ailes laterales ; 
ils ont pris l’apparence de feuilles, et la feuille veritable 
serait adnee a la base. 5 Further, these ‘branches’ are sup- 
posed to be homologous with bracts — members, which (Debat 
says) ‘ suivant une theorie generalement admise . . . sont des 
pedoncules floraux modifies par l’epanouissement d’un limbe.’ 
To the bract the true leaf (i. e. one of the vaginant laminae) 
has become adnate by one margin. 
It will be sufficient here to point out that Debat’s state- 
ment as to the structure of the young leaf is not correct, 
as the very youngest leaves that can be dissected from the 
buds of F. adiantoides do possess at this stage — in common 
with other species of Fissidens — vaginant laminae, although 
this part is at the time very minute and relatively quite 
disproportionate in size. This fact is well seen in F. serru- 
latus , Brid. In the fully grown leaf of this species the 
vaginant laminae reach halfway the length of the leaf ; 
in the young leaf, however, at about the time of cessation 
of apical growth, the relative size of the different parts is 
as shown in Fig. 40. To understand how this occurs, it is 
I 
