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BOTANY: H, H. M. BOWMAN 
water and in various soils. The mangrove, growing as it does in such 
peculiar conditions, in salt and fresh water alike, offers a rich field for 
studies on absorption and transpiration rates, the effects of chemical 
substances on these phenomena, and the physical relations of density 
of media. A brief account is here given of some of the more impor- 
tant observations made on the effects of these changes in media on the 
transpiration. 
The material used was Rhizophora seedlings. These were selected 
as the most easily handled and the most readily procurable. Seedlings 
one to two years old, growing on shores of keys from 3 to 75 miles from 
the Tortugas, were secured and planted, some in Tortugas sand (a 
coarse sand composed of broken shell, corals, and other calcareous 
debris) and others in a ferruginous sandstone soil brought down from 
New Jersey. Another series also was planted in fine calcareous mud 
taken from the moat at Fort Jefferson. These cultures compose the 
soil series of experiments. 
Another group of plants was planted in the Tortugas sand and kept 
in water of the following concentrations: 100, 75, 50, 20, 10, and 5% 
fresh, and 100% salt water. In a previous season records were taken 
on plants grown in hyperconcentrated sea-water, 140% salt. The 
record for these plants gave a very slow rate of growth, and after lin- 
gering for a few weeks, the plants yellowed, dropped the leaves, and 
died. These experiments were not repeated. 
In all these cultures the plants were grown in large 10-inch beakers 
and the water was siphoned off every day and a fresh solution was put 
on. This was found to be necessary to keep algae and mosquito larvae 
out of the cultures and also to simulate the tidal action in daily bring- 
ing a fresh supply of water to the plants, as in their natural habitat. 
Still another group of cultures was made of plants kept in various 
light intensities as well as moisture conditions. One class was kept in 
New Jersey soil in partial shade with 100% salt water; another in par- 
tial shade, New Jersey soil, 50% salt water; a third class, kept in par- 
tial shade in shell sand, merely moistened with 100% salt water; a 
fourth class was kept in partial shade in New Jersey soil, merely mois- 
tened with 100% salt; and a fifth class in full sun all day long, planted 
in shell sand and kept moist with 100% salt water. 
This last class was in a condition which most nearly approximates 
the natural environment of Rhizophora seedlings cast up by the waves 
on a coral strand in the Gulf region. The tides bury the hypocotyl or 
it bores a resting-place by the radicular end twirling in the water-cur- 
rent and often becomes entirely covered with sand. Leaves are put 
