Mabch 17, 1911] 



SCIENCE 



415 



nisli the mechanical or molecular energy at 

 the disposition of the plant, they are the least 

 understood of the climatic elements. In the 

 tropics the light conditions are very intense 

 and for this reason actinometric studies are 

 especially necessary in tropical countries. 



As for the chemical intensity of light, such 

 comparative work as that of Roscoe and 

 Thorpe in England, Portugal and Brazil 

 opens up naost interesting vistas of research. 



While we have valuable results from tem- 

 perate climates in regard to the relation of 

 plants to soil moisture, evaporation and asso- 

 ciated phenomena, we know practically noth- 

 ing about these conditions in the tropics. 



We know that in the tropics the average 

 annual temperature differs but little, while 

 the quantity of precipitation differs largely. 

 The latter feature is . of greater importance 

 and needs therefore special study. We have 

 a large amount of scattered data and much 

 generalization, but practically nothing of 

 definite scientific or practical value. 



Tropical soils are as yet very little studied, 

 except in a few localities, as in the West 

 Indies, British Guiana and Java. The rapid 

 decomposition of rock caused by the combina- 

 tion of abundant moisture and heat furnishes 

 new layers of soil as well as a fascinating 

 subject of study for the geologist and the 

 chemist. 



The numerous vegetable products of the 

 American tropics are as yet very little knovm 

 from a scientific point of view. There are 

 ■scores of tan barks, dozens of oil-producing 

 plants. New rubber plants are found fre- 

 quently in the neotropical regions. New and 

 old tropical fruits invite study, and economic 

 plants generally occur in abundance. 



When we consider that tropical America 

 has given mankind more economic plants than 

 any other part of the world, it seems strange 

 that, after all, tropical America is less known 

 to-day than any other region of the earth. 

 We may only mention corn, potatoes, cacao, 

 tobacco, rubber, sisal hemp, vanilla and prob- 

 ably bananas among the important vegetable 

 products of the western hemisphere. 



There is an open and very profitable field 



for the plant breeder in improving tropical 

 products. 



The tropics are inhabited by peculiar and 

 interesting races of mankind, and traces of 

 ancient civilizations are now obliterated by a 

 luxuriant forest vegetation, which clothes the 

 tropical lands from the level of the sea to the 

 summits of the loftiest mountains. The an- 

 tlu-opologist and the ethnologist find in trop- 

 ical America some of the most complicated 

 and interesting problems of research. 



It is in the tropics where the principal vol- 

 canic belts encircle the globe, and with their 

 variety of geological structure, their frequent 

 earthquakes, their coral formations bathed by 

 the tepid waters of the great tropical oceans, 

 the tropics of America offer unequaled oppor- 

 tunities for geological studies. 



The violent electric discharges in the tropics 

 produce atmospheric nitrogen, which probably 

 is carried by the rain water into the soil, and 

 thus contributes to and probably explains some 

 of the fertility of the tropical soils. Our 

 knowledge in this regard is very limited. 



Where the tropics teem with vegetable prod- 

 ucts of the most striking diversity, animal life 

 also is most abundant and of great variety. 

 Tropical zoology is so far only touched on the 

 surface, and especially are the lower forms of 

 animal life in the equatorial zone known only 

 slightly. 



The pathogenic bacteria have only in a few 

 instances been investigated and a large field is 

 here open. There has been much progress in 

 tropical medicine during late years, but while 

 we know the elements of this science there is 

 still much to learn, many tropical diseases to 

 study and many remedies to discover. 



Modern science has demonstrated that life 

 in the tropics is possible for white man, and 

 if ordinary precautions are taken he is as safe 

 there as in any other place. Tropical explora- 

 tion has craved its dues in form of many 

 martyrs to science, but with modern appli- 

 ances and present-day knowledge there is no 

 need of privations and exposure during trop- 

 ical travels. 



In this regard it is of special importance 

 that systematic research in the tropics be 



