Bruchns-infestcd Beaiis. 379 



aborted in a very curious manner, but this may possibly 

 have been due to other causes. The appearance of these 

 unproductive pods may be seen by the coloured sketches 

 which I now exhibit, and which were most carefully 

 drawn to scale from accurate measurements. 



The total produce, therefore, of four out of the five 

 varieties experimented upon was so greatly diminished 

 as to leave no possible ground for doubt that the 

 presence of the weevil in the seed is highly detrimental, 

 affecting to a very considerable degree the reproductive 

 powers of the future plant. At the same time, we have 

 the curious fact that the number of weevils present, 

 whether one, two, three, four, five, or even six, appears 

 to influence but slightly the health of the plant and its 

 produce, the mischief being apparently caused by the 

 mere presence of the weevil, almost irrespective of its 

 numbers in any individual case. It is also remarkable 

 that certain of the diseased plants — if diseased we may 

 justly term them — bore even more than the normal 

 number of pods. This latter fact would seem to point 

 to the conclusion that the amount of damage sustained 

 by infested seed depends in some measure upon the 

 position of the burrow. If the germ itself be penetrated 

 the seed must necessarily be rendered sterile ; and it is 

 not impossible that the nearer the burrow is situated 

 with regard to the germ the greater is the consequent 

 injury. This point I hope to clear up in the course of 

 future experiments. 



It would also be both interesting and instructive to 

 sow uninfested seed produced by diseased plants in order 

 to ascertain whether the injury is transmitted in any 

 degree to the second generation. This experiment I 

 should myself have attempted, but that I was informed 

 by Messrs. Carter that seed-beans of the more delicate 

 varieties will not ripen in the English climate, but are 

 principally imported from Southern Spain. And, as 

 these varieties are those which suffer most severely from 

 the presence of the beetle, I judged it useless to attempt 

 the experiment with the more robust varieties only. 



With regard to the aversion manifested by Aphis 

 rumicis for the sap of the weakened plants, the almost 

 total absence of the insect in this neighbourhood during 

 the present season afforded me no op[)ortuiiity of making 

 further observations upon the subject. I found specimens. 



