Sept. 1896.] ROTTENNESS OF TURNIPS AND SWEDES. 



131 



and prepared in dry weather and kept as dry as possible. The 

 pits ought not to be placed on the same spot year after year, 

 and the roots should be carefully examined to see that none 

 with even the slightest sign of decay are stored among the sound 

 ones. 



The fungus gains an increased power of infection in each 

 successive root, and hence has an exceptional ability to work 

 destruction when the roots are closely in contact with each 

 other in the pits. 



The frost is answerable for a certain amount of damage 

 independent of that caused by the fungus ; but severe freezing 

 does not destroy the vitality of the conidia, in fact the hyphae 

 penetrate the roots killed by frost more rapidly than sound 

 ones. 



Note. — It must not be supposed that Botrytis is the only 

 parasite attacking the roots ; other fungi and bacteria play their 

 part, but the life-history of these forms is still under investiga- 

 tion. 



Explanation of Figures. 



1. Conidiuin of Botrytis with germ-tube (a) (mag.). 



3. Cell of swede with two conidia sown on the surface of the exposed 

 cell-wall ; the conidia have germinated and forced the germ- 

 tube into the cell 18 hours after sowing (mag.). 



3. A similar piece of swede showing the conidia and developing 



mycelia ; 24 hours after sowing (mag.). 



4. Young conidiophore with one branch near the apex (mag.). 



5. Young conidiophore showing the further development of the 



branching (mag.). 



6. Branching of conidiophore showing the small projections upon 



which the conidia are developed (mag.). 



7. Conidiophore and partially developed conidia (mag.). 



8. Conidiophore with clusters of ripe conidia (mag.). 



9. Portion of the turnip in Fig. 10 showing the ramification of the 



fungus among the cells (mag.). 



10. White globe turnip infected with Botrytis at the cut (a) on the 



right-hand upper surface. Grey mould is seen near the cut and 

 the fungus has almost destroyed the root as shown by the shaded 

 portion in the centre (slightly reduced). 



11. Portion of dead potato-haulm with sclerotia (a) (nat. size). 



12. Potato-haulm with sclerotia germinating and producing tufts of 



Botrytis (nat. size). 



13. Conidiophores and conidia from one of the sclerotia on the potato- 



haulm (X 16). 



O 93016. 



B 



