167 



exclude wingless insects that can only visit the flowers by ascending 



the corolla is closed by small scale-like appendages, in some flowers 

 tufts of hairs perform a similar office thus excluding small insects 

 which are poor pollen carriers, hut admitting the Leak or proboscis of 



columbine, have long narrow spurs which secrete their nectar in the 

 remote extremity, thus favoring the visits of insects with long pro- 

 bosces, but effectually keep their nectar from those with short ones. 

 But occasionally this exclusiveness is resented. Insects with stout 

 mandibles, finding the nectar beyond their reach, eat holes through 

 these long spurs or long corolla tubes and thus get at the nectar 

 surreptitiously. To guard against such thieves some plants have 

 inflated calyces or inflated bracts which clasp the base of the corolla 

 tube and thus protect it. But time will not permit us to extend our 

 examination of this subject any further or to examine more minutely 

 its details. Enough has been said to indicate that even a moderate 

 knowledge of it must add greatly to the interest with which we view 

 the almost endless \ariatioiis in floral structures. All the beautiful 



singular appendages and strange marKings, mine ngntoi un> mo.j«... 



to an end which would otherwise escape us and leave them in our 

 estimation as mere curious shapes and whimsical or unmeaning colors. 

 We learn from it the explanation of many phenomena which would 

 otherwise be inexplicable. Plants kept in houses or in conservatories 

 are often sterile. They are excluded from the visits of pollen carriers 

 and are therefore infertile. The question is sometimes raised why 

 seedlings raised from the seed of a single apple tree should bear fruit 

 so diverse from that of the parent tree and from each other. It is 

 very common to find a half dozen different varieties of apple trees in 

 a single orchard. The blossoms of any one tree in an orchard are 

 likely to be fertilized by pollen from half a dozen different kinds G f 

 apple trees. Is it any wonder then that the fruit of seedlings thus 

 produced should vary greatly ? The natural tendency to variation is 

 in such a case much aided by inherited variation. 



When the squash was introduced into the Sandwich Islands it was 

 found impossible to raise squashes unless the pollen was transferred by 

 hand from the stamens to the pistils. There were no natural pollen 

 carriers in the islands. At length a ship loaded with logwood arrived 

 in port and in one of the hollow pieces of wood there happened to be 

 a nest of humble bees. These escaped to the islands and soon stocked 



