1897. NOTES AND COMMENTS. 155 



species of Coleospovinm) may be recognised at some little distance by 

 their pale yellow leaves and general thinness of growth. The colour 

 is due to the effects of the fungus, which is confined almost entirely 

 to or near the tips of the needles formed the previous season. The 

 thinness of growth is owing to the lack of leaves, all except those of 

 the previous year's growth having fallen prematurely. 



The writer finds that the fungus is propagated by sporidia which 

 appear on diseased leaves at the same time as the new leaves. The 

 sporidia develop only in wet weather, and are washed or drop from 

 those on which they are borne on to the young needles just showing 

 their tips. The latter show no signs of infection for two or three 

 months, and it requires twelve months to complete the development 

 of the fungus. During a large part of this time it does not seriously 

 interfere with the functions of its host-leaf. As soon, however, as it 

 ruptures the tissues, loss of water is increased to about one-fifth above 

 normal ; the reserve water in the cells is gradually used up, loss of 

 turgidity, and other physiological changes follow, resulting in the 

 gradual death and casting of the leaves. 



Experiments on the rate of loss of water from diseased and 

 healthy parts of the same leaf show that, before the fungus has 

 ruptured the cortical tissue, transpiration is less from the infected areas. 

 This is found to be due to the permanent closing of the stomata, and 

 may result in keeping the diseased parts alive longer than the healthy 

 when a leaf or branch is removed from the tree. 



Drunk and Incapable. 



In a recent number of the Journal of Botany, J. L. Williams 

 describes various observations made in North Wales on the intoxica- 

 tion of humble-bees by the honey of certain composite plants, and 

 the relation of their consequent movements to the pollination of the 

 flower. The bees were seen greedily sucking the honey from heads 

 of flowers of Scabiosa and Cenfaurea, after which they were incapable 

 of flying away, and rolled helplessly about in the flower-head, or fell 

 to the ground. On recovering from their debauch, after a few minutes 

 they immediately flew to another plant of the same species and began 

 afresh. During their struggles the bees became covered with pollen, 

 and on visiting a second plant were very effectual agents in impreg- 

 nating its flowers with pollen from the one previously visited. Mr. 

 Williams suggests that this method of cross-pollination may in time 

 become normal. Hitherto its occurrence has been uncertain, and was 

 only observed a second time after an interval of five years, when the 

 writer was unable to obtain sufficient honey for analysis, so that the 

 cause of intoxication is unknown. Whether or no advantages may 

 accrue to the plant from thus * drugging ' the nectar which it offers 

 to insect visitors, the comparative frequency of such effects cannot be 

 denied. Nor are they confined to members of families like Composites 



