536 
On Tropical Epiphytes. (Septembei, 
horses, and two to three yards in length. These consist of 
thread-like shoots, coiled spirally, withered at their base, 
and arising from a single twig. Such a one, torn from its 
seat by the wind or by birds, twines round the branch of a 
tree and sends out shoots freely suspended in the air. The 
plant propagates itself only in this asexual manner, whilst 
most other Bromeliaceae produce numerous seeds, which 
readily germinate on the rind of trees. The plant is covered 
with scale-like hairs, through which liquids can very readily 
penetrate into its tissues, whilst the rest of the epidermis is 
relatively impermeable. The spoon-shaped bases of the 
leaves always contain water and putrescent organic matters 
which— as it has been experimentally proved— are not merely 
utilised by the plant, but are necessary to its existence. 
The leaves of Tillandsia bulbosa appear admirably adapted 
to its peculiar conditions of existence. The leaf-sheath 
forms here a bulb-like organ, always containing water and 
dead inserts. As it closes nearly air-tight the water is not 
lost even in an inverted position. The plant is theiefoie in no 
need of negative geotrupism. The water penetrates into the 
cavity by capillary attraction. The interior of the leaves is 
lined with numerous absorbent scales. _ 
Dr. Schimper appends a sketch of the connexion between 
the vital relations and the geographical distribution of the 
Inessential conditions of a luxuriant growth of epiphytic 
plants are light and moisture. It is therefore most splendidly 
developed in narrow clearings in the mountain forests and 
on the banks of woodland streams. The epiphytic vegeta- 
tion of dry localities— the “ Savanna flora ” according to 
Schimper— is characterised by the predominance of scaly 
Bromeliaceae, which therefore appear white or grey. In the 
primaeval forests there are more Bromeliaceae with tendei 
leaves In more open parts of the woods there occur re- 
presentatives of the Savanna flora. On the other hand, we 
find on trees in the Savannas not seldom forest Epiphytes, 
though for the most part smaller and less luxuriant. In 
artificial clearings in the drier parts of the woods we may 
observe how the forest Epiphytes gradually give place to the 
Savanna forms. The latter have probably been developed 
out of emigrants from the primaeval forests. Otherwise we 
must assume a very recent immigration of the former, since 
within historical times the West Indian Islands were wooded 
down to the water’s edge. . . . a 
The texture of the bark of their host has also an influence 
upon the physiognomy of the epiphytic flora. A baik full of 
