16 



THE POLLINATION OF PEAR FLOWERS. 



relati\'ely few anthers open in the night, as coolness and moisture tend 

 to retard their opening. The warmth and dryness which follow sun- 

 rise doubtless open large nuuibers Avhich have become ready duriug 

 the night. 



If not gathered by insects the polleu gradually becomes dry and falls 

 oft'. When ilowers are inclosed in bags there is always an abundance 

 of pollen on the anthers until the petals fall. Generally the flower does 

 not drop its ])etals until three or four days after all the anthers are 

 burst. The blooming period for each flower is from five to seven days. 

 The whole time of blooming, from the day the first floAvers open until 

 the larger part of the petals are on the ground, is generally from eight 

 to nine days. There is considerable difference in the date of blooming 

 of different varieties, a matter that will be discussed later. The flowers 

 of any one variety generally bloom well together. On the first day 

 a few flowers will come out; the next day finds the tree white with 

 bloom; four more days of fine Aveather and the pollen Avill be about all 

 shed and the Avork of pollinatiug by insects practically finished. Where 

 bees and other insects are numerous the flowers are abundantly a isited, 

 and each flower during its life is undoubtedly visited several times. 

 Judging from the pollen on the anthers and from the number of insects 

 continually at work on the trees in the orchard at Rochester, the floAvers 

 were visited at least six times daily. In 1801 trees at Washington 

 Avere observed that were visited even more frequently. Darwin esti- 

 mated that some flowers in his garden were visited twenty times daily. 

 There is no doubt, as Miiller states, that the pollen readily falls on the 

 stigmas if insect visits do not occur. Even if insects do visit the flower 

 some of its own i)ollen Avill i)robably reach its stigmas. The flower is 

 normally turned sideways, and the stigmas are about the same length 

 and surlounded closely by the numerous stamens, which often nearly 

 touch the stigmas, so that they could hardly miss being self-pollinated. 

 When an insect first visits a pear tree, after coming from another 

 A^ariety, it has adhering to its body the pollen of that variety, but 

 after having alighted on one or two flowers, it becomes dusted Avith 

 the new variety of i^ollen in addition. Each stigma, therefore, is 

 probably dusted with more or less of a mixture of pollen. The only 

 Avay for the pear flowers to derive the benefits of cross-pollination f 

 and avoid tbe evils of self-pollination is to refuse to accept the pollen (, 

 of their own kind and to respond to the cross-pollen. We shall see 

 later that this is precisely what occurs. 



Even before the petals fall it may be observed that the young fruits 

 of some of the flowers are beginning to swell. Whether this is due to 

 their natural vigor or to the fact that they show at that early date the 

 effect of fecundation, I am not x>repared to say, but the latter seems 

 the more probable. Some of the flowers never begin to develop their 

 fruits^ but after remaining oii the tree four to six days fall to th^ 



