WJLCHURA OK HXBBIDS. 



59 



under favourable circumstances, be still efficient after fourteen 

 days, while that eight days old may be trusted implicitly. 



The seeds of willows germinate very rapidly, and lose their 

 vitality with proportional rapidity. The pollen-grains, indeed? 

 sometimes preserve their vitality longer than the seed. This 

 quickness of germination arises from the fact that the embryo is 

 already richly supplied with chlorophyll, and that the testa is very 

 thin and transparent, while there is not a trace of albumen. They 

 soon dry up if they are not in contact with moist earth ; they 

 should therefore be sown as soon as they are ripe, and in from 

 twelve to twenty-four hours the cotyledons make their appearance. 

 Care must be taken not to water the young plants too heavily, or 

 the delicate seedlings may be washed away. Our author's plan 

 was to raise the plants in pots, which could be supplied with 

 water from below, and easily protected from the access of any 

 strange seed. They were allowed to remain in this situation till 

 they were some inches high, and then transplanted into the open 

 air ; and thus plants sown in May obtained a height of two or 

 three feet by the end of summer. The smaller kinds generally 

 flowered in three years, the larger, but not arboreous species, in 

 about four. Scattered catkins, however, sometimes appeared on 

 two-year-old plants, and in one instance a plant sown in June 

 produced flowers when ten months old. 



Our author adds a remark on the use which he made of natural 

 hybrid willows during the course of his experiments. They 

 seemed to be of the greatest importance as regards hybrids com- 

 posed of more than two factors. By their help he was enabled to 

 raise two hybrids (of which admirable nature-printed figures are 

 given at the end of the volume) compounded of six different spe- 

 cies, which he believes, after seven years' experience, to have been 

 impossible with artificial hybrids. 



An example is added of the composition of hybrids of more than 

 two species, the parents being a spontaneous hybrid of S. Lap- 

 ponum and S. silesiaca, a spontaneous hybrid of S. purpurea and 

 S. viminalis, with an artificial hybrid of S. eaprea and 8. dapJinoides. 

 The circles in the following scheme indicate the male, the squares 

 the female, and the triangles the father and mother plants of the 

 free hybrids or species indifferently. 



