196 



STRUCTURAL BOTANY 



growing-point. The bulb appears at first as a lateral 

 growth at one side of the base of the cotyledon. The 

 main root may attain a length of a couple of inches, 

 but it sends out few, if any, rootlets. Its function is 



only temporary, for it is soon 

 replaced by adventitious roots 

 arising from the base of the 

 bulb. After a time the bulb 

 sends up green foliage-leaves 

 (Fig. 94); the cotyledon de- 

 cays, leaving only its base ; 

 the seed, the endosperm of 

 which is now exhausted, is 

 reduced to an empty shell, 

 and germination is now 

 ended. 



In some Lilies, and in 

 many other plants, both 

 Monocotyledons and Dicoty- 

 ledons, the base of the stem 

 is brought to its proper 

 FIG. 94. Seedling of a Lily depth in the ground by the 

 &FZRS&&Z. contraction of the roots. In 

 leaf. c.R, contractile adven- L. Mar tag on the young bulb 



of ground. Natural size, drawn down year by year, 

 owing to the shortening of 



the adventitious roots. As the end of the root- 

 attaches itself firmly to the soil, the effect of the 

 contraction is to exert a downward pull on the bulb 

 The upper part of the root is alone capable of con- 

 traction, and is much thicker than the rest. The 



