282 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
might easily be extended and with a more thorough study might 
furnish an interesting question as to the rapidity of multipHcation of 
these plants and as to the means by which they hold their own among 
the more rapidly multi])l}ang plants. As to the question why certain 
plants are found on one slope and not on another, the palms as an 
example may explain. At an altitude of 500 or more meters, palms 
of various kinds are scattered about among the other forest vegetation. 
This occurs, however, only on slopes to the northeast, that is, exposed 
to the northeast trades. The opposite sides at this high altitude 
present an ordinary forest front undotted by a single palm. ^Moisture, 
then, either by its immediate presence or in its relation to the winds 
very probably is a factor in the distribution of all the plants. 
So far as methods of distribution are concerned it may be said that 
there are very few special adaptations to dispersal. Ccnchrus echinatus 
seems to be the only one adapted for dispersal by means of its prickly 
fruit, which adheres to animals. The various members of the Bigno- 
niaceae and of the Asclepiadaceae are suited for wind dispersion as 
are also Gossj'pium and Bombax. Of course there is no limit to the 
carrying of seeds by birds from one valley to another so that the 
absence or presence of moisture is probably the most potent factor 
restricting the mountain plants to the mountain and the lowland 
plants to the lowlands. 
The further question as to the distribution of the jilants according 
to season is quite as interesting as the distribution of the plants in the 
various topographical regions. There is a striking difference in the 
appearance of the plains, the hills, and the valleys as seen in the rainy 
season and in the dry. In the rainy period the fields are carpeted with 
green and the bushes and trees are heavy with foliage and bright with 
blossoms. In the dry season the fields are almost devoid of stick or 
leaf and many bushes and trees are to every appearance dead. When 
the rains come on in July or August, Tribulus terrestris and Kalsiroe- 
mia maxivia cover the roadsides and plains; Stack y tar phda coccinea 
and S. jamaicensis, Spermacoce tenuior, Argemone mexicana, Asdepias 
curassavica, and many others form a rank growth of weeds in the 
coconut groves and cane fields; various shrubs of the hillside, Capparis 
verrucosa, Cassia emarginata, Bauhinia cumanensis, and others are 
out in leaf and in flower; and the climbing shrubs and vines form a 
luxuriant growth along the "rio" beds. In the dry season only a few 
of these plants can be foimd in flower. It is noteworthy that in several 
