10 MEMBERS OF PLANTS. 



shoots are to turn to it ; and heiice, when Dutrochet 

 caused a misseltoe seed to germinate on the inside of 

 a window pane, it sent its root inwards towards the 

 apartment; when on the outside of the pane it did 

 the same. Hence it is that hyacinths grow better in 

 water glasses of a dark colour, than in uncoloured ones. 



It may be from this inexplicable Jaw, perhaps, that 

 all roots tend more or less towards the centre of the 

 earth ; yet Grew, and recently Dutrochet, found that 

 when French beans were placed in a suspended box, 

 with earth above them and holes below to admit light, 

 they sent their roots down through the holes into the 

 light, and not into the earth in the box. Mr. T. A. 

 Knight placed French beans in moistened moss on 

 revolving wheels, and found that both when the wheel 

 was vertical and when it was horizontal, the radicles 

 were directed outwards towards the circumference. 



No root, it is said, is of a green colour, which can- 

 not be produced even by exposure to the light ; though 

 by this means green branches may be made to spring 

 from roots, and potatoes exposed to light become 

 green, though their rootlets will not. 



Besides sucking in nutriment from the soil, roots 

 give off refuse or indigested matter, as may be seen in 

 the case of hyacinths grown in water. This appears 

 to be the chief cause, that plants will not grow well 

 successively in the same soil unless changed by rota- 



(1) This will be explained in the "ALPHABET OF SCIENTIFIC 

 AGRICULTURE," under Rotation of Crops. 



