688 
Cross-fertilisation of Cereals. 
15, fig. 1). The sudden opening of the flower is due to the pres- 
sure of the included organs. The short cells of the filament are 
ready to elongate, the feathery stigmas are pressing, while the 
lodicules (two little scales at the base of the flower, 5 and 9, 
fig. 1) are waiting to expand. At the same instant each of these 
organs exerts its influence : the filaments, pushing the anthers 
before them, extend to three or four times their former length ; 
the feathery stigmas spread themselves in the air ; and the bases 
of the lodicules rapidly swell. 
The forces thus suddenly and simultaneously exercised as 
speedily exhaust themselves, and the glumes return to their 
former position, covering in the fertilised stigmas ; while the 
filaments, unable to support the heavy anthers, double over the 
glumes and hang outside. The very slight attachment of the 
filament permits the anther to be shaken by the least movement 
of the wind, and it is in this way speedily emptied of all the 
remaining pollen grains, and these may be carried by the wind 
to the stigma of the flower of another plant. But the simul- 
taneous ripening of the stamens and stigma and the partial dis- 
charge of the pollen on the stigma before the flower opens show 
that self-fertilisation is the rule in the wheat. Observations in 
the field confirm this view, for in experimental grounds where 
different varieties of wheat are grown in close proximity in 
parallel rows, no accidental cross-fertilisation due to wind-carried 
pollen grains has been observed. 
It is obvious that the work of cross-fertilising wheat or 
barley is an extremely delicate operation. It has to be per- 
formed on the living plant in the open field. The flower is 
difficult to deal with, being supported on a long, slender, and 
easily moved straw; the parts of the flower are small, and the 
organs operated on are extremely delicate. The stamens must 
be removed before the pollen grains are ripe, and the stigmas 
must be protected from the access of pollen grains from the 
flowers of the same spike or of neighbouring plants. The appli- 
cation of the pollen grains to the feathery stigma is a delicate 
work, and should be done, when possible, by applying the ripe 
pollen grains direct from the anthers to the stigma by gently 
moving them over its surface. Many an experimenter has been 
baffled by the difficulties or has been disappointed at the mixed 
results. The more credit is due to those who have preserved 
and succeeded?. 
The pollen grains are efficient for fertilisation in proportion 
to the closeness of affinity between the plant which produced 
them and that to which they are applied. The affinities of the 
plants which by natural or artificial fertilisation have produced 
