Sept. 1895.] 



INJURIOUS INSECTS AND FUNGI. 



181 



" A. Experiments conducted in a Sterilised Solution of Stable 



Mmiure. 



" 2. The contents of two flasks were infected by adding 

 crushed tubercles of a diseased cabbage root. Two per cent, of 

 a saturated solution of potassium hydrate was added to the 

 contents of one flask, and two per cent, of commercial sulphuric 

 acid to the other. A young cabbage plant free from disease was 

 then placed in each flask. At the end of two months the plant 

 in the flask containing potassium hydrate was growing vigorously 

 and perfectly free from disease, whereas the plant growing in 

 the solution containing sulphuric acid was badly diseased, much 

 more so than check plants growing in infected soil free from 

 acid, for the same period of time. Similar experiments made 

 during successive years always yielded the same result. 



" 3. Two young cabbage plants showing decided symptoms of 

 disease were placed in flasks containing the same proportions of 

 potassium hydrate and sulphuric acid respectively as in Experi- 

 ment 2. At the end of two months the plant growing in the 

 solution containing potassium hydrate appeared to be perfectly 

 healthy, the indica,tions of nodules present on the root at the 

 commencement of the experiment having become eflfaced by 

 subsequent ^rowth. The plant growing in the solution 

 containing sulphuric acid was badly diseased. 



" Similar results were obtained in Experiments 2 and 3, when 

 potassium hydrate was replaced by ammonium hydrate, and 

 sulphuric acid by hydrochloric acid. 



" 4. Two diseased seedling cabbages were placed in separate 

 flasks of the sterilised solution. The liquid in one flask was 

 saturated once a week with carbonic dioxide, the contents of the 

 second flask not being interfered with in any way. At the end 

 of two months both plants had the disease developed to the 

 same extent, proving that carbonic acid is neutral as regards the 

 development of PLasmodiophora. 



" B. Experiments conducted with Sterilised Soil. 



" 5. Two pots of soil, sterilised by steam, were infected with 

 the crushed roots of diseased cabbages. The soil in one pot was 

 mixed with quicklime ; that in the other with bone manure, 

 having an acid reaction. A healthy cabbage seedling was 

 planted in each pot, and at the end of two months the plant in 

 the pot containing lime was perfectly healthy, whereas the 

 plant in the soil containing acid bone manure was badly 

 diseased. 



" 6. Two pots containing soil mixed with quicklime and acid 

 bone manure respectively had a diseased cabbage seedling placed 

 in cache At the end of two months the disease was more 

 developed in both seedlings than at the time of planting ; 

 proving that the presence of lime will not arrest the disease 

 when the plants are once attacked. 



