[Vol.. 2 



312 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



Laestadia Theae) cause but small losses of tea leaves in our 

 colonies. 



The sugar-cane evidently is the crop which is most subject 

 to the attack of fungi. This becomes clear when we look upon 

 the method of propagating the saccharum. Small pieces of 

 the cane stem are used as cuttings, which are put into the 

 soil. The soft pith, rich in sugar, is an ideal substratum for 

 fungous growth, and we must not be astonished that even 

 saprophytes enter it. Thielaviopsis ethaceticus and Colle- 

 totrichum falcatum are two typical destroyers of sugar-cane 

 cuttings. 



Bacterial diseases are scarcely to be found. I will admit 

 that more bacterial diseases may be discovered, but up to 

 the present time the only bacterial disease of importance is 

 the tobacco wilt due to Bacillus Solanacearum, the same 

 trouble which occurs in the United States. The same bacillus 

 also causes a disease of peanuts. Probably the gum-disease 

 of sugar-cane is also caused by bacterial. It is curious that 

 algae in some cases (Cephaleuros virescens) cause diseases 

 of tea and coffee plants, as they kill not only leaves but, as is 

 true in the case of tea, also the twigs. 



Here I have come to the end of the list of fungous troubles. 

 Compared to the fungous diseases of the United States and 

 even to those of Europe, those of the tropics are smaller in 

 number. Tropical agriculture might be compared to the 

 agriculture of the United States more than to that of the Old 

 World. Vast areas are covered with one crop and often with 

 one variety of a crop, so far as we know anything definite 

 about varieties and races of tropical plants. In the subtrop- 

 ical regions of the United States, where at certain times the 

 temperature equals that of the tropics, the air is much drier 

 and there is a certain change of temperature, even in the 

 region of eternal spring in California, which is foreign to the 

 tropical climate. In the tropics of Asia and the subtropics 

 of the United States insect troubles have assumed immense 

 proportions, but as to fungous diseases, these are of more 

 importance in the subtropics of the New World. 



