MASTIGOPHORA. 21 



become amcebulas, and are found, often several together, in the 

 parenchyma cells feeding on the sap. The plant-cells mul- 

 tiply and become abnormally swollen, and many hypertophry. 

 Shortly the amoebulfe in each cell fuse together and become a 

 Plasmodium. Later the nuclei of the plasmodium break up 

 into chromidia, part being destroyed, part reconcentrated to 

 form generative nuclei. These divide by karyokinesis, and 

 then the protoplasm collects around the nuclei to form small 

 uninuclear bodies called gametes, which fuse in pairs. These 

 zygotes then become surrounded by a tough wall to form round 

 spores, which pass into the soil on the decay of the plant, and 

 later give rise to the minute flagellulse from which the attack 

 originates. 



The Plasmodium seen in the cells is a yellowish stringy slime, 

 which may wholly or only partially fill the cell. By October 

 this Plasmodium has broken up into spores which closely pack 

 the swollen cells. 



Prevention and Treatment. — It is very important after an 

 attack to have as far as possible all cabbage stumps and all 

 diseased material burnt. 



Land subject to this disease should be heavily limed, the 

 lime being in as finely divided state as possible. As it only 

 attacks cruciferous plants, ceasing to grow them on the land 

 for two or three years will check it materially. 



CLASS II. MASTIGOPHORA. 



These have one or more permanent organs serving for loco- 

 motion or for capture of food in the form of flagella in the 

 adult stage. They are divided into four sub-classes : 1. Flagel- 

 lata ; 2. Dinoflagellata ; 3. Cystoflagellata ; and 4. Silico- 

 flagellata. 



The family Trypanosomatidm are the most important, and 

 they belong to a division of the Flagellata known as Mona- 

 didea, small protozoa of simple structure with one or more 



