Hybridization and Crossbreeding 271 
the top of this is a more or less rounded knob called the 
stigma, which is slightly roughened on the surface. By 
the time the stigma is matured the ovules are fully formed 
and ready for fertilization. 
In nature, pollination, and afterwards fertilization, take 
place by the agency of bees and other insects, and some- 
times by the agency of wind. Self-pollination is sometimes 
effected. 
We must get a clear idea of pollination and fertilization 
before we can go further. Pollination means simply the 
transferring of the pollen from the anthers to the stigma, 
whereas fertilization is the union of the nucleus of the pollen 
grain with the nucleus of the ovule. This takes place some 
time after pollination. In the case of Pines it takes place 
nine months after pollination has been effected. In other 
cases it only takes a few weeks, a few days, or even a 
few hours. 
When the plants to be improved have been selected, 
the first thing is to see that there is no chance of pollina- 
tion being effected except in the way desired. Therefore 
the anthers should be cut from the Bowers which are re- 
quired to produce the seed, thus preventing self-pollination. 
The flowers must be protected with small muslin bags, to 
prevent insects from effecting cross -fertilization. Then, 
when the stigma is matured, it may be safe to go over 
the flowers two or three days in succession with the pollen 
from the anthers of the flowers desired to be crossed, 
putting it on the ones selected as seed-bearers. If, how- 
ever, the petals of the flow r ers being pollinated have 
dropped, it is a sign that fertilization has taken place. 
It is a good plan to cross-pollinate the plants. That 
