640 LABORATORY EXERCISES 



outline is suggestive of such study, where the heading suggests the question whicli 

 the students ask themselves in their examination of the diseased plants. 

 Serial number of type. Place of collection. 



Habitat and soil condition. Date. 



Name of host. Common names of disease. 



History and geographic distribution. 

 Additional data (Here may be given the nature and amount of loss). 



SYMPTOMS 



Under this head should be described the general structural changes (morphologic, 

 or histologic) which are manifest in the diseased host plant, and which distinguish it 

 from a healthy individual. They may be treated under the following captions: 



1. General appearance of the diseased plant. 



2. Change in form of part diseased. 



3. Change in taste and odor. 



4. Change in color as contrasted mth healthy part. 



(a) Pallor (chlorosis), yellow or white instead of normal green. (Do such 



names as mosaic, calico and yellows apply?) 

 (t) Colored spots or areas on leaves, stems, fruits (black, brown, orange, 



red, variegated, white, yellow, etc.). 



5. Perforation of leaves (shot-hole). 



6. Damping-off, wilt, wilting, blight (blossom-blight, body-blight, leaf-blight, 

 twig-blight). 



7. Death of leaves, twigs, stems, etc. (necrosis). 



8. Dwarfing or atrophy. Several names have come into current use expressive 

 of such condition, as: curly dwarf, leaf -roll, little-peach, spindling-sprouts. 



9. Increase in size: hypertrophy. Measurements should be made of the en- 

 larged parts as contrasted with the normal and the foIlo\ving names may be found 

 applicable in the study of the hypertrophy: crown-gall, root-gall, root-knot, root- 

 tubercle. 



10. Replacement of parts by new parts. 



11. Mummification, character of . 



12. Change in position of organs. 



13. Disappearance or non-formation of plant parts. 



14. Excrescences and malformations. The following names may be found 

 suggestive in the description of excrescences and malformations: Cankers, corky 

 outgrowths, pustules, rosettes, scabs and witches' brooms. 



15. Exudations. 



Slime flux. 

 Gummosis. 

 Resinosis. 



16. Rotting. — The following terms are suggestive of some kinds of rot: bud-rot, 

 collar-rot, crown-rot, foot-rot, heart-rot, root-rot, stem-rot and the following par- 

 ticular kinds given prominence here. 



