40 PLANTING BULBS AND TUBERS. [CHAP. III. 



the dahlia and the potato, and solid bulbs or 

 corras, such as those of the crocus, they regard 

 as underground stems. 



These distinctions, however, though they 

 may be interesting to the botanist and vege- 

 table physiologist, are of little or no use in 

 practice ; the practical gardener treating bulbs 

 and tubers exactly alike, and planting them as 

 he would sow a seed : that is to say, he fixes 

 them firmly in the ground, and covers them, 

 but not so deeply as to exclude the air. In 

 preparing a bed for hyacinths or other tunicated 

 bulbs, it is necessary to pulverise the soil to a 

 much greater depth than for ordinary seeds ; 

 as the true roots of the hyacinth descend per- 

 pendicularly to a considerable depth, as may be 

 seen when these plants are grown in glasses. 

 The very circumstance of growing hyacinths in 

 glasses, where they vegetate and send down 

 their roots exposed to the full influence of the 

 light, appears contrary to the usual effects of 

 light on vegetation ; and, indeed, the plants are 

 said generally to thrive best when the glasses 

 are kept in the dark till the roots are half 

 grown. This practice, however, retards the 

 growth of the leaves and stem, and often in- 

 jures the developement of the flowers ; and, at 

 any rate, it is quite certain that hyacinths in 

 glasses should never be kept in darkness after 

 their leaves have begun to expand ; as, if there 

 be not abundance of light to occasion rapid 

 evaporation from the leaves, the plants will 

 soon become surcharged with moisture from 

 the quantity constantly supplied to their roots, 



