CONTRIBUTIONS FROM THE W ISLEY LABORATORY. 15 
CONTRIBUTIONS FROM THE WISLEY LABORATORY. 
XXXVIII. — Pollination in Orchards (vi.). 
Pollen-Carrying Agents. 
By A. N. Rawes, Fruit Experiments Officer, and G. Fox Wilson, 
F.E.S., N.D.H., Entomologist. 
It has been shown on p. 8 that all varieties of apple "set " best when 
pollinated from other varieties. The same is true for most British 
fruits. In planting fruits it is therefore desirable to intermix 
varieties, in order to render the transference of pollen from one variety 
to another easy. 
The carrying of pollen from flower to flower is sometimes attributed 
to the wind, sometimes to insects, and among the latter hive bees are 
often looked upon as the only active agents. Our own observations 
at Wisley, begun by the Director in 191 2, and in the past few years 
carried on by us, lead us to believe that the wind plays no part in 
pollination of fruits (except in nuts and perhaps mulberries), and that 
several other insects beside hive bees are very active. 
The wind as an agent. —In order to ascertain whether the wind 
played any part in carrying pollen, glass slips, rendered permanently 
sticky by smearing with glycerine, were suspended at varying distances 
from apples, pears, and plums in full bloom. In very few cases were 
pollen grains of fruit trees found upon them after they had remained 
suspended for one to three days. Pollen of pines and other plants nor- 
mally dependent upon the wind for pollination was found in abundance 
on some occasions. On the few slips bearing pollen of the fruit trees, 
the grains present were in masses of several together, not scattered 
as was, for instance, the pine pollen. These masses had evidently 
been left by an insect alighting upon the slip, for in some cases a leg 
was left behind as well ! 
These observations are only in accord with expectations, for the 
conspicuous flowers, small stigmas, and sticky pollen of fruit trees 
contrast with the well-known adaptations for wind-pollination 
found in such plants as the hazel. They are, moreover, confirmed by 
observations made abroad. They indicate clearly that the wind is 
not an active agent in the distribution of fruit-tree pollen. 
Insect agents. — There is no question that hive bees, where they are 
numerous, and in suitable weather, are indefatigable workers in fruit 
flowers, and therefore active agents in carrying pollen. But they 
are by no means the only agents, and in fact this work may be most 
efficiently performed by other insects. 
Annually, for some years past, the apple crop at Wisley has been 
