THE INFLUENCE OF BEES ON CROPS. 265 



they are entirely 'absent. Again, in localities where some 



species of plants are found, certain species of insects are also to 

 Ije met with, and rice versa. Thus, particular plants are dependent 

 on certain insects, and particular insects on certain plants, for the 

 propagation of their species. 



The pollen-bearing organs are not always to be met with in 

 the same flower. In the melon, cucumber, and other plants belong- 

 ing to that tribe, some of the flowers are male — i.e., possess stamens 

 only, or have no pistil; while others are femiale — i.e., possess a 

 pistil but no stamens. The pollen of this tribe of plants is com- 

 paratively heavy and viscid. It is therefore obvious, as the two 

 sexual flowers are situated at some distance the one from the other, 

 a foreign agent must convey the pollen from the stamen to the 

 •stigma of the pistil of the female flower. In some of the Egyptian 

 palm-trees there are what are termed male and female trees — i.e., 

 the sexual flowers are on separate and distinct trees. The trees 

 are often at considerable distances the one from the other, and the 

 pollen can only be transported by insects. The variegated laurel 

 (Auniba Ja/jonica) is another of these dioecious sarubs, and of 

 course, like the palm-trees referred to, the male and female flowers 

 are on different trees. It was introduced into England many years 

 ago by the Dutch from Japan. It so happened that the plants 

 first introduced were female plants, or in other words bore female 

 flowers only. There were no pollen-bearing flowers, conseqviently 

 no seed could be produced, and propagation was carried on by cut- 

 tings only. Some years afterwards a Mff Fortune introduced some 

 male plants. These were planted in close proximity to some of the 

 x)ld Dutch ones that had been perpetuated by means of cuttings. 

 The result was that an abundance of fertile seed was produced 

 the following season. 



The pollen of the variegated laurel was an article of commerce 

 in the London Convent Garden market. 



The length of time the pollen of some of the palms and laurels 

 retain their vitality is remarkable. The pollen in other varieties 

 £»f plants must be utilised soon after it is discharged from the 

 Anther or its procreative property is lost. 



The quantity of pollen grains discharged from flowers is soine- 

 thing enormous, especially in those plants where the sexual flowers 

 are on different trees. The flowers on a Chinese laburnum 

 {Wistaria r/ii'nensis) were calculated to contain no less than twenty- 

 iieven billions of pollen grains. 



