MICROLEJEUNEA BULLATA 165 
late in upper part; perianth pyriform, 0.4 mm. long, 0.2 mm. wide, 
rostellate, sharply five-keeled, smooth: ¢ inflorescence occupying 
a short branch, often proliferating at the end; bracts in two to 
four pairs, larger than the leaves, imbricated, strongly inflated, 
subequally bifid with a very shallow sinus, the lobes rounded at 
the apex and entire; bracteoles similar to underleaves, present 
only at base of spike. 
Type-locality, St. Vincent (Guilding). 
On bark: South Carolina (Sullivant); Florida (J. D. Smith, 
Mrs. Russell, Underwood, Straub). Found also at various places 
in tropical America. 
Exsic.: Hep. Amer. 132 f. p. (as Lejeunea (Colo-Lej.) minu- 
tissima). 
Microlejeunea bullata is our smallest representative of the 
Lejeuneae. It has not before been recorded for the United States, 
but seems to be common in Florida. When growing by itself its 
minute size makes it almost invisible, but as it often grows in com- 
 pany with other species it has been collected several times. The 
type-specimens agree closely with those from Florida. 
According to Lindberg, M. ulicina occurs in Sullivant's Musc. 
Alleg. 272, mixed with Zejeunea Americana. In one example of 
this exsiccata examined by the writer, there seems to be no ad- 
mixture whatever; in another example there is a single sterile 
stem of M. bullata, and it is probable that Lindberg confused this 
species with M. ulicina. At all events it seems advisable to omit 
the latter species from our lists until its presence is more definitely 
established. 
M. ulicina is about twice as large as M. bullata, its leaves spread 
a little more from the axis and tend to be more pointed, the 
cells of the lobe are considerably larger, averaging 18 ۸ in diame- 
ter, the cell-walls are thicker and usually show minute trigones, 
while the lobules are relatively smaller. The perichaetial bracts 
of the two species, except for the difference in size, resemble each 
other very closely, but the bracteole of M. ulicina is entire or 
nearly so, while that of M. bullata is crenulate or denticulate. 
M. bullata has also been confused with Cololejeunea minutissima, 
with which it often grows. The presence of underleaves will at 
once distinguish it from this species, and there is little danger of 
confusing it with any of our other Lejeuneae. 
