80 



THE POLLINATION OF PEAR FLOWERS. 



pear flowers may possibly have been developed for the purpose of 

 attracting flies. 



The effect of climatic conditions on the abundance of insect visitors 

 is an exceedingly striking and important matter. Warm, sunny weather 

 favors insect visits, while cool or rainy weather interferes seriously with 

 them. Yery often when the sun is shining the air is too cool for bees 

 to work. Eain, of course, drives all insects away. Even signs of rain 

 alarm the bees. I have frequently seen a whole day of cool, sunny 

 weather when only a few flies and beetles could be found on the flowers. 

 While cool weather probablj?^ retards the flowers somewhat, yet tlie 

 number of days of oi^en flowers is probably limited, and this time is lost 

 by the flowers as far as cross-pollination is concerned. The amount of 

 nectar secreted by the flowers is also greatly affected l)y the weather 

 and varies enormously, from almost nothing to very large drops, which 

 sometimes overflow the nectar cup and fall to the ground at the 

 slightest jar. This influences very strongly the insect visits. 



DISEASES. 



Diseases afl'ect the setting of fruit, (1) by injuring the general 

 health and vigor of the tree, and (2) by directly attacking the 

 flowers and young fruits. Leaf-blight {Eiito)nosporium inaculatum) 

 often does considerable injury by checking the growth and i)remature]y 

 defoliating the trees. The obscure root rot enfeebles the growth of 

 the tree, turns its foliage yellow, and stunts its growth. A healthy tree 

 when first affected usually bears a heavy crop of under-sized fruit, and 

 if it survives another season it refuses to bear. 



In I^ew York the scab fungus (Fusicladmm pyriniim) often causes an 

 almost complete destruction of the young fruits of tlie Seckel and some 

 other susceptible varieties. It attacks the young fruits even before the 

 petals have fallen, and often completely covers them with its growth, 

 so that the fruit dries up and turns black. 



Pear blight not unfrequently plays sad havoc with the blossoms, 

 especially in the South. This disease, which is caused by an exceed- 

 ingly minute microbe, spreads from flower to flower by means of 

 insects. It multiplies in the nectar, and the insect visitors that dip 

 their mouth parts in the infected flowers carry the infection to those 

 which they afterwards visit. In this way whole orchards of Le Conte 

 and Kieffer i^ears, especially the latter, have their flowers destroyed. 



In addition to fungous diseases the insect enemies do their share of 

 injury. In most cases, however, insect injuries are recognized as such 

 by the grower and frequently the insect can be found. 



GENERAL SUMMARY AND CONCLUSIONS. 



In the pollination work on the pear two distinct kinds of experiments 

 have been tried j (1) sim]3le bagging experiments, in which bags of 



