THE DEVELOPMENT AND RELATIONSHIP OF 
MONOCLEA.' 
CONTRIBUTIONS FROM THE BOTANICAL LABORATORY OF 
THE JOHNS HOPKINS UNIVERSITY, No. 2. 
DUNCAN S. JOHNSON. 
(WITH PLATES XVI AND XVII) 
WHILE studying and collecting the native Piperaceae of Jamaica, 
in the spring of 1903, I also preserved plants in various stages of 
development of the liverwort Monoclea Forsteri Hook. The results 
of the study of the material of this little known form are given in the 
following pages. : ; 
Monoclea occurs in Jamaica chiefly on wet rocks and banks in the 
mountain forests (CAMPBELL ’98). The most luxuriant growth of it 
seen by the writer was one of many meters in extent in a small depres- 
sion near New Haven Gap in the Blue Mountains. This depression 
was filled up considerably by living and decaying vegetation, but the 
water in it stood at such a level that the tangles of Monoclea and 
associated plants were practically floating upon its surface. The 
appearance of a mat of Monoclea is not so much like one of the more 
attenuated plants of Marchantia or Fegatella as it is like a mat of 
gigantic Pellia, though the edges of the thallus are often more crisped 
or curled upward than in the latter genus. The plants growing in 
the water at New Haven Gap were often 3°™ wide, in the case of the 
broader branches, while elsewhere they seldom exceeded 2°". The 
Stowing ends of these aquatic plants were almost erect, apparently 
because of the wet substratum, since this peculiarity did not seem to 
be attributable to the direction from which light reached them. 
A majority of the plants found were sterile, and in the case of the 
plants growing in wetter situations fertile plants were very scarce. 
In groups of plants growing in the damp ravines, where the substratum 
Was not so completely saturated with water, though the air was satu- 
tated with-water vapor, fertile plants of both sexes were easily found. 
we investigation pursued with the aid of a grant from the Botanical Society of 
190 
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