Antillean Region: Puerto Rican District. 683 
Pico del Valle is three to four feet high (1—2 m), consisting of shrubs such 
as Lyonia heptamera, Garrya Fadyenit, while here are found Peperomia reflexa, 
Pilea alpina, and the ferns Vittaria lineata, Polypodium angustifolium, Elapho- 
glossum Eggersü, E. leptophyllum, Asplenium monanthes, Lepicystis murorum, 
mosses and lichens. The other mountains peaks of which there are many in 
the island are veritable terra incognita, to reach which the botanist is compelled 
to slash his way through thickets of ferns, lianes and shrubs often so dense 
that he must crawl on hands and knees through a tunnel cut by himself, and 
blinded by spores at every step. 
D. Puerto Rican District. 
The islands of Puerto Rico, Culebra, Crab, St. Thomas, St. John, 
Tortola, Virgin Gorda, Anegada and the adjoining keys together with 
St. Croix are phytogeographically included in this district. Geographically 
St. Croix is separated from the other islands by a sea passage, 2,452 fathoms 
deep; whereas the greatest depth of sea between Puerto Rico and the other 
islands mentioned does not exceed 23 fathoms and that in the Virgin Passage 
(see ante p. 124). These islands are all mountainous, projecting above the 
water as submerged peaks, which they really are. ‘They are very rugged, 
due to the encroachment of the sea which has formed cliffs, detached stacks 
and skerries, with winding channels of blue water, like land-locked lakes bet- 
ween the islands. The smaller islands are marked by stretches of coral and 
shell-sand overgrown with seaside grapes, cactus — a large prickly pear. 
St. Croix has a high, sharp configuration with deep cliffs near the shore and 
many low hills in the interior all covered with beautiful vegetation. Two 
areas are distinguished: the Puerto Rican Territory and the Virgin Island 
Territory. 
a) Puerto Rican Territory. 
This territory comprises the island of Puerto Rico, Culebra and Crab Island. 
Puerto Rico, which is rectangular in shape, possesses a central mountain 
chain known as the Cayey range extending unbroken from end to end of the 
island with the Luquillo Range, parallel to it on the south (see ante p. 124). 
Between the two ranges (2,500 feet) lies a mountainous valley full of sharp 
ridges, detached peaks and deep ravines, with no level land except a few 
narrow alluvial valleys.. Along either coast, extending from the foothills of 
the mountains to the sea, stretch beautiful plains, gently sloping to the shore 
and reaching in width at some points on the south side to five miles and on 
the north side to three miles. 
Very little is known concerning the plant formations of Puerto Rico except 
the tropic forest formation, and consequently no description of them can ‚be 
given, except for several which have recently been studied. The following 
account summarizes our knowledge of the phytogeography of the island. 
