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POPULAR SCIENCE REVIEW. 
the same branches as the catkins, and are also in clusters of 
from two to six or eight (the future nuts), and are of equally 
simple structure with the male flowers, being formed of a single 
pistil enclosed in bracts, the ovary surmounted by from three to 
five stigmas, the bright crimson threads by which these female 
flowers are recognised. If one of these crimson threads is 
placed under an ordinary pocket lens, it will generally be found 
to have on its surface several apparently minute particles of 
dust, which, on further examination, are found to be pollen- 
grains which have been blown from the male flowers. Each in- 
dividual pollen-grain has the power of emitting a ‘‘ pollen- 
tube,” which penetrates the stigma, reaches the ovary, and by 
the fertilisation of the ovule induces the formation of the 
embryo, and thus the development of the ovule into the fertile 
nut. Since the only means by which the pollen can be con- 
veyed from the male to the female flower is the agency of the 
wind, and it is only quite by chance that any of the grains can 
reach their destination, the reason is obvious of the enormous 
amount of pollen with which the catkins of the hazel are fur- 
nished. In some plants, the fertilisation of which is effected in 
the same manner, the quantity of pollen is still greater, and 
this is especially the case in the Coniferse or fir-tribe. If a yew- 
tree is struck with a stick or agitated by the wind at the time 
when the pollen is being discharged, it will rise in the form of a 
dense smoke, giving the impression of a burning bush; and 
American travellers have described how the water of some of 
their lakes near the shore is covered at certain seasons by a 
thick stratum of a sulphur-like substance, the pollen blown from 
the neighbouring pine-woods. Whether the female flowers of 
the hazel are fertilised from the catkins on the same or on a 
different bush is a point still in dispute. 
Another instance in which there is little doubt that fertilisa- 
tion is accomplished by the agency of the wind, though botanists 
are not quite unanimous on this point, is that of our common 
cereal crops, and especially of wheat. Important in the highest 
degree from a mere mercantile point of view as is any question 
connected with the production of our corn crops, it is only very 
recently that any reliable observations have been made on the 
mode in which the flowers of wheat are fertilised ; but these 
have led to some very curious results.^ When a field of wheat 
is in flower, that is, in ordinary seasons, in the early part of 
June, each ear will be found to be furnished with a great 
number of purplish anthers hanging at the ends of filaments of 
extraordinary delicacy, or rather of empty anther-sacs from 
which every grain of pollen has been discharged. These anthers 
* See “Gardener’s Chronicle,” March 15 and 22, and May 24, 1873. 
