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BOTANY 



PART I 



tracted strongly and so altered the position of the bulb that the higher 

 roots appear curved near their attachment. When the bulb has 

 reached the proper depth it is only drawn down each year to compen- 

 sate for the onward growth of the growing point. In other cases all 

 the roots are not contractile (Arum), or only one or a few contractile 

 roots are developed (Crocus, Gladiolus, Oxalis elegans). While the above 



FIG. 207. 1-k, Germination of Lilium martagon (reduced). The horizontal line marks the surface 

 of the soil ; the vertical line is graduated in centimetres. 1, Seedling attached to seed ; 

 2, plant at end of the second year ; 3, young plant still descending in the soil ; A, full-grown 

 plant at its normal depth. 5, Colchicum autumnale (somewhat reduced). The original 

 position of the tuber, which has been altered by the contraction of the roots, is shown by 

 the dotted outline. 6, Contracted root of Lilium. (x 6. After RIMBACH.) 



examples are of lateral roots a similar result may be brought about by 

 the main root. Thus in some rosette plants the main root continues 

 to contract as secondary growth proceeds, so that the growing point of 

 the shoot is drawn down each year as much as it is raised by its own 

 growth, and the rosette of leaves remains pressed against the surface 

 of the soil (e.g. Gentiana lutea). 



3. Annual herbs do not retain their vegetative organs during 

 the unfavourable season, which they pass safely in the form of dry 

 seeds. 



