A. 8. IIoRNK AND H. M. Lkfrov 371) 



Aleurodes. Fig. 5. 



No. 1. 22.3. 12. Four pots were placed on soil under a bell-jar raised on inverted 

 pots; 20 flies from Salvia and 24 from potato were liberated under the jar, some 

 escaping. 



5. 4. 12. Eggs seen on the leaves; the plants were clean, healthy and similar 

 in appearance. 



17. 4. 12. Scale first observed. 



24. 4. 12. Young flies observed. 



5. 5. 12. Many scales on the leaves, a few empty, the first flies having emerged. 

 There are no symptoms to record ; the leaves are not spotted nor noticeably yellow. 

 The control plants, grown under similar conditions but without insects, do not diifcr 

 from the infested plants. 



No. 9. 23. 3. 12. Four pots on soil, under bell-jar raised on inverted pots, with a 

 double muslin curtain containing soil round the lower part of the jar and resting on 

 the soil. Sixty-seven flies from Salvia were liberated. 



5. 4. 12. Many eggs on the leaves, some dark, some yellow. Two dead flies 

 seen with a cloud of white threads (? hyphae of a mould). Photographed 9 o'clock. 



5. 5. 12. Good infestation of scales. The leaves are slightly yellow as compared 

 with the control kept under similar conditions. There are no other observable 

 symptoms and the leaves are clean, not curled, and well grown. 



All the plants infested with Aleurodes were kept free from Red 

 Spider and Aphides. 



Experiments set up out of doors were unsuccessful because the 

 plants were killed by frost. 



Aleurodes. Gross infestation. 



During the course of the experiments described above, the whole 

 of the plants raised at Wisley from the January sowing, and not used 

 for the infestations with individuals, had been kept in a cool frame 

 arranged in series according to the method of potting, kind of soil and 

 origin of the seed. Aleurodes soon appeared amongst them and was 

 allowed to increase unchecked. All the plants were examined critically, 

 one by one, on May 8, and there was noted by one observer the amount 

 of Aleurodes and Aphis, and by the other the characters of the plants 

 themselves, for example, height, whether upright or procumbent, size 

 and shape of juvenile and adult leaves, and the presence or absence 

 of blemishes, such as blotches, pinkness, discoloured veins, yellow- 

 ness, etc. 



The first three series, potted in coarse soil, in large pots, will be 

 considered together since no attempt is here made to draw deductions 



25—2 



