66 THE BOOK OF NATURE STUDY 



new plant to the soil best suited to it. Kerner mentions a 

 species of Garlic (A Ilium paterfamilias}, the old bulb of which 

 gives rise to a hundred young ones in a year. Naturally they 

 could not all develop, if they remained crowded together ; by 

 contractile roots the young bulbs are drawn away from the old 

 one. Only a few of the roots, he says, strike downwards ; by 

 far the greater number grow out parallel to the soil. With this 

 species maybe compared the behaviour of another garlic, A Ilium 

 ursinum, very common in woods and easily recognised by its 

 strong smell. In early spring, it forms a circle of fleshy roots, 

 which grow obliquely downwards. As soon as they are firmly 

 attached to the soil, they contract to about two-thirds of their 

 original length, and thus draw the bulb downwards. In the 

 autumn another set of roots is developed. These grow 

 outwards, and their work is to get nourishment for the plant. 

 Then follows the period of winter rest, and the following spring 

 another circle of contractile roots is developed to drag the bulb 

 downwards. Other plants which have contractile roots are 

 the Ranunculus bulbosus and young Raspberry bushes, these 

 latter in contracting form spiral coils. 



The Bluebell is specially interesting. In the month of May 

 bulbs will be found with large roots, 4 or 5 inches in length, 

 transversely wrinkled in the upper region. The lower portion of 

 the root being firmly fixed in the soil, the upper part contracts 

 and pulls the bulb underground. 



Tulip bulbs develop droppers or sinkers. A dropper is a 

 continuation of the base of the foliage-leaf. It emerges from the 

 bulb by boring its way through the scale leaves enclosing it. It 

 is not a solid structure, but a hollow tube containing in its swollen 

 tip a small knob. Figs. 38 and 39 give drawings of two droppers 

 very unlike each other externally. The difference in length is 

 due to the age of the Tulips. Short droppers are characteristic 

 of older Tulips ; the slender dropper probably belongs to a young 

 seedling, and would have swollen up a good deal by the end of the 

 year, if it had not been disturbed. It is by means of droppers 

 that some bulbous plants, particularly Tulips and Squills, prevent 

 overcrowding and protect themselves from frost in winter and 

 drought in summer. The Tulip with the short dropper in Fig. 38, 



