Evans: HeEpaticAE oF Puerto Rico 21 
times extending as far as the end of the keel, which in many cases 
curves forward and meets it. The extreme development of this 
type of lobule is seen especially well in D. crucianella ( pl. 4, f. 13) 
but is also found in D. dédens and in other species. The lower edge 
of the lobule is here adnate in its outer part to the postical surface 
of the lobe, giving rise in this way to a short and rudimentary 
wing which is scarcely a cell broad and only one or two cells 
long. The adnate portion of the lobule is itself only two or three 
cells long and a single cell wide ; its terminal cell, although attached 
at its base to the lobe, projects at its apex asa distinct tooth which 
meets the curved tooth at the apex of the lobule. These two 
teeth, together with the sinus of the lobule, form a circular open- 
ing into the water-sac. We find among the Puerto Rico Drepano- 
Zejeuneae all gradations between this extreme development of the 
lobule and that seen for example in D. sabulata, where the terminal 
cell is only slightly curved and does not reach the end of the keel. 
We must bear in mind, however, that the development of the lob- 
ule is very dependent upon external conditions and that we fre- 
quently find specimens in which the typical lobular characters of 
the species are not clearly indicated. 
Although ocelli are not usually found in Drepanolejeunea, no 
fewer than six of the Puerto Rico species exhibit them. They are 
never conspicuous and their number (in the vegetative leaves at least) 
never exceeds two. Even in species in which they are normally 
present, many of the leaves, especially those which are poorly de- 
veloped, fail to show them. The ocelli in most cases are no 
larger than the neighboring cells and usually retain their angular 
form even when their contents become lifeless. They are distin- 
guished by the granular or fatty bodies which they contain and do 
not usually become hyaline and empty as in many other Lejeuneae. 
Sometimes the addition of potash solution brings them out more 
clearly. With regard to the uses of these ocelli practically noth- 
ing is known, although it is probable that they sometimes take 
part in the formation of the water-sac as in Leptolejeunea exocellata. 
It is not at all likely, however, that they are ever the empty 
mother-cells of disc-shaped gemmae as in certain species of Co/o- 
lejeunea and probably of other genera. Drepanolejeunea in fact 
seems never to develop gemmae of this type but reproduces itself 
