TRANSACTIONS OF WAGNER 
3964 VEGETATION OF SOUTH FLORIDA 
trunks. Other vegetation is scant. Various lianes struggle to the tops of the 
trees to reach the sunlight and include a kind of gourd and a high-climbing dew- 
flower, Commelina, which with its stout fleshy stems and branches climbs over 
the limbs of the pond-apple trees, often reaching to the highest branches. The 
main forest of custard-apple trees south of the lake consists of a close stand 
of trees 9 meters (30 feet) tall, forming a dense shade, so that a twilight pervades 
these solitudes. The branches are twisted and interlocked and the crown is 
therefore very dense. The undergrowth is close, so that it is with difficulty 
that one can penetrate the forest (Plate X, Fig. 1). Three ferns are conspicu- 
ous on the ground. A rare fern, new to Florida, Meniscium serratum Cav., 
was collected by me, as also the large tropic fern, Acrostichum aureum L. and 
Dryopteris patens (Sw.) Kuntze. All of these ferns, in sporulation on June 
22, were growing out of the rich, black humus covering the deep muck of the 
Everglades. This fact suggests the natural succession of vegetation, the cus- 
tard-apple trees invading a saw-grass strip, so that the custard-apple forest is 
subsequent to a saw-grass marsh in the region under discussion. The south- 
ern elder, Sambucus intermedia Carr., in full flower on June 22 occupied the 
more open and therefore lighter parts of the forest. Two herbs, however, are 
noteworthy as growing in almost pure associations on the forest floor. In one 
place, we find Persicaria (Polygonum) punctata (Ell) Small covering the 
ground, in other places Commelina erecta L. is exclusive. Two other herbs are 
important elements of the herbaceous contingent, viz., the false nettle, Boeh- 
meria cylindrica (L.) Willd.,and Jussiaea peruviana L., while the moon-flower, 
Calonyction (Ipomoea) aculeatum (L.) House, climbed up the trees, especially 
on the lake, or open, side of the forest where it covers every available support 
in dense hanging masses. ‘Two epiphytes were dislodged from the tree 
branches with a pole. An epiphytic orchid in flower June 22, Epidendrum 
tampense Lindl. ( Encyclia tampense (Lindl.) Small, is common on the cus- 
tard-apple trees, as is also the fern Polypodium polypodioides (L.) A. S. Hitchc. 
(=P. incanum Sw.) (Plate X, Fig. 1). It seems that the custard-apple, or 
pond-apple tree, is extremely sensitive to frosts, and its growth in a narrow 
strip along the south shore of Lake Okeechobee is to be explained by the ame- 
liorating effect of the large, shallow body of water, which warms up rapidly in 
the sun, lying to the north and west of the southern shore line of the lake (see 
map). 
A letter of query directed to Dr. W. E. Safford, who has monographed the 
