126 EvANS: TAXILEJEUNEA PTEROGONIA 
sides of the sinus are usually bounded by only six or seven cells 
instead of by eight to ten as in 7. pterogonia and T. jamaicensis. 
It will be seen at once that all these differences are vague and 
unsatisfactory, being found in very variable organs. 
A more important distinction is found in the greater size of 
T. densiflora. This is indicated by comparing FIG. I with FIG. 12, 
the latter of which is magnified about 40 per cent more. The 
leaf-cells are also considerably larger (compare Fic. 14 with PLATE 
—, Fic. 4) and are further distinguished by their very poorly 
developed thickenings. The trigones in fact are often absent 
altogether and, even when present, are minute and have concave 
sides, so that they can be discerned only with difficulty. Inter- 
_mediate thickenings are absent altogether or very vaguely indi- 
cated, and there seems to be no trace of the minute verruculae 
found in the other two species. Perhaps the poorly developed 
thickenings are associated with the wet conditions under which 
the species develops. 
The bracts and bracteoles (Fics. 18-22), except for their 
larger size and laxer structure, have little to distinguish them 
from those of T. jamaicensis, and it has already been shown how 
vague the distinctions are between this latter species and T. 
pterogonia. In T. densiflora it is rare to find a bract which is 
wholly without teeth, although these may be very vague, and the 
lobule is rarely anything more than a basal fold, with or without 
a distinct apex. The teeth on the sides of the bracteole are 
somewhat less in evidence than in either of the other two species. 
4. TAXILEJEUNEA DEBILIS (Lehm. & Lindenb.) Steph. 
Jungermannia debilis Lehm. & Lindenb. in Lehmann, Pug. 
Piant.’4: 51. — 1832. 
Lejeunea delilis Nees & Mont. Ann. Sci. Nat. Bot. II. 5: 60. 
1836. 
Omphalanthus debiis Lehm. & Lindenb. in G. L. & N. Syn. Hep. 
306. 1845. _ 
Omphalanthus martinicensis Gottsche, Ann. Sci. Nat. Bot. V. 1: 
149. 1864 (in obs.). 
Lejeunea (Taxilejeunea) debilis Steph. Hedwigia 29: 141. 1896. 
