12 DISEASES OF TROPICAL PLANTS CH . 



in fact some of them are so small that they cannot be 

 seen singly without the use of a microscope. Many of 

 these non-seed-producing plants are responsible for the 

 diseases of the higher plants, and thus seriously interfere 

 with both great arid small agricultural industries of the 

 world. 



The plant kingdom may be subdivided into the 

 following groups : 



ALGAE Live in the water and possess chlorophyll, 

 although many of the salt-water forms and some fresh- 

 water forms possess other colouring matters which 



Thallophyta 



conceal the chlorophyll. 



FUNGI Plants without chlorophyll and living either 

 parasitically or saprophytically on other organisms. 



Bacteria. Minute organisms possessing some of the characters of 

 fungi and living either parasitically or saprophytically. 



Slime moulds. Organisms possessing some of the characters of 

 fungi, and some characters of the lower animals. 



Pteridophtya. FILICES Ferns, etc. 



Spermatophyta (seed- /GYMNOSPERMA Cone-bearing plants. 

 bearing plants) (ANGIOSPERMA True flowering plants. 



All of these groups of plants contain chlorophyll 

 (the green colouring material) except the fungi, bacteria, 

 and slime moulds. The presence or absence of this 

 chlorophyll makes a decided difference in the habits and 

 life of the plants. Those possessing chlorophyll are 

 able to lead an independent existence if provided with 

 the necessary soil, water, sunlight, and heat ; while those 

 which do not possess it must live parasitically on living 

 plants and animals, or saprophytically on dead and 

 decaying organic materials. 



It will be readily seen that this work relates more 

 especially to the Spermatophytes, which are of such 

 great importance to mankind, and to the fungi, bacteria, 

 and slime moulds, which are responsible for so many of 

 the diseases of the Spermatophytes. 



The green plants obtain their food supply from the 

 air, the water, and the soil. In order to do this they 



