182 
VEGETABLE PB0DUCTI0N8. 
this Istlimus possesses over any point hitherto selected further 
south, lying in the equatorial zone. Each isothermal zone has 
its peculiar zone of vegetation. These (25 in number) have been 
classified by Professor Schow. 
The Isthmus is placed under the 15th region, or that of the 
cactus and pepper families, because these are the predominating 
ones found growing there. The mean temperature of this bo- 
tanical region varies from 68° to 84° F., and includes among 
others the cultivated species : Zea M. sorghum, jatropha, diosco- 
rea, convolvulus, arracacha, marauta, musa, mangofera, amoma, 
psidium, cocos, carica, persica, bromelia, Anacardium, tama- 
rindus, citrus, passiflora, tlieobroma, vanilla, coffea, sacchamm, 
lycopersicum, capsicum, cajanus, ojrachis, opuntia, nicotiana, 
and gossypium. 
From the northern shore to the base of the Sierra on the 
south, the vegetation is that found arising from the alternating 
influences of heat and moisture. In the rainy season, the rivers 
which drain the Atlantic plains overflow their banks for a con- 
siderable distance, and disseminate over a vast extent of country 
a variety of soluble saline matter, with such animal and vegetable 
substances as are suspended in the w T ater during that period. 
These borders, therefore, constantly increasing in richness, are 
densely studded with plants which exhibit a large and spongy cel- 
lular tissue ; those which possess broadly expanded, soft leaves, 
furnished with a great number of cortical pores, or those whose 
growth is rapid, and which by depositing little oily or resinous 
matter are less liable to the deteriorating influences of constant 
humidity. Among these may be classed the cascalote, castarica, 
encina (live-oak), guanacaste, guayabo, huacillo, javicue, jobo, 
macaya, mangle, palo-baria, roble, sangre-draco, and the cres- 
centia cujete, or Indian cup-tree. 
On all the rivers are seen huge specimens of these most valu- 
able trees of the equinoctial regions, mingled with a hundred 
varieties of palmoe, gracefully towering above plants of the most 
dense and impenetrable foliage, whose masses of verdure sweep 
the current at every sinuosity, and either thwart the efforts of the 
stream or deflect its course. Under these circumstances the 
view which is presented to the eye is often of the most enchant- 
