— 38 



i 



\ 



their normal diameter. The branches are short, few in number and are produced 

 near the end of the conidiphores. On germination, the conidia give rise to zoo- 

 spores. Oospores are also developed. 



Control. — Bordeaux mixture will usually keep this disease completely 

 under control. Self-boiled lime — sulphur may also be used. Infected leaves,! 

 mummies, and other refuse which harbour the oospores should be burnt. 



KEY TO THE COMMON GENERA OF THE PERONOSPORACEAE. 



A. Conidia at first produced at the end of the conidiophore, but are pushed t 

 the side as the fertile tips swell and continue their growth — Phytophthora 

 AA. Conidia always at the end of the conidiophore. Tips of conidiophore 

 branches do not continue to grow after conidia are formed. 

 B. Conidia germinate indirectly by means of zoospores. 



C. Oospore free from wall of oogonium — Plasmopara. 

 CC. Oospore adherent to the wall of the oogonium. Conidiophore; 

 short, irregular — Sclcrospora. 

 BB. Conidia germinate directly by means of a germ-tube. 



C. Ferriie tips arise from disk -like swelling. Germ passes out through 



terminal papilla — Bremia. 

 CC. Fertile tips branch-like, usually in pairs. No terminal papilla, 

 germination lateral — Peronospora. 



INSECTS OF 1913 



E. Melville Du Porte, Macdonald College. J 



The season of 1913 was a remarkable one in this district on account of the 

 long continued drought. There was little rain and that fell in small quantities 

 which soon evaporated from the parched soil. Official records ait Macdonald 

 College show that during the five months from ]\Iay to September, the rainfall 

 amounted to only 9.7 inches. This was distributed over 43 showers and as a 

 light shower evaporates before the water has been able to sink very far, it can 

 be readily seen that the precipitation was not a very effective one. 



The temparature was moderate throughout the season. 



Several forms of vegetation suffered severely, as an immediate result of 



the drought, and many from the ravages of destructive insects, to the rapid 



multiplication of which the season seemed to be conducive. Several injurious 



insects were abundantly in evidence last season and also several predaceous or 



parasitic forms. 



The influence of the weather conditions on the number and prevalence of 

 phytophagous insects has not, as far as I know, been exhaustively studied. 

 A bright, dry season with moderate rainfall favours their increase, whereas 

 a very wet season has the opposite effect. Dr. Forbes of Illionois, says that in very 

 wet weather "the sap of the plant may become so dilute, through excessive ab- 

 sorption of water by the roots that it loses its nutritive value and insects depend- 

 ent on it are not so well nourished as by the denser sap of a plant growing in a 

 dryer soil. They consequently grow less thriftily and multiply less abundantly, 

 and may even diminish rapidly in numbers during a wet season, while if the 



