8i 



NOTES ON THE BLUEBELL. 



T. W. WOODHEAD, F.L.S., 



Technical College, Huddersfield. 



(Continued ironi p. 48.) 



Many bulbs were found much elongated in form, some 

 measuring two to three inches in length, and throughout the 

 greater part not more than inch to 3/^ inch thick (Fig. 4, c and 

 d). Commonly they taper from above downwards, forming a 

 shape very suggestive when considered in connection with the 

 function of the contractile roots. In July the base of the bulb 

 still further enlarges, but does not equal the apex in diameter. 



In a section of an elongated bulb at this period (Fig. 4, d) 

 the scale leaves are seen to be thickened, especially at the 

 base and tip, the inner being tubular, and enclosing the foliage 

 leaves. 



A long series of bulbs was obtained, from small globular to 

 much elongated forms. Plate V., Fig. 7, shows a selection of 

 these. The first external sign of elongation is a shallow annular 

 constriction near the base. This is the region of active growth 

 in which the lower portions of the leaf bases are mainly con- 

 cerned. From very numerous observations of bulbs under 

 cultivation, as well as in the woods, we find that the upper 

 swollen part of the bulb is not forced upwards during elongation, 

 but downwards. In addition to this we have the action of the 

 contractile roots, the lower portions of which are firmly fixed in 

 the soil by their root-hairs'^ (Fig. 5, a and b). Here we have an 

 interesting example of response to environment, the bulbs being 

 stimulated according to their position relative to depth, air and 

 light, being 'endowed with irritabilities by means of which they 

 grow through the substratum . . . like true roots.' f Ultimately 

 the requisite depth is attained, but in the meantime changes 

 have begun towards the formation of a typical globular bulb. | 



I have not as yet been able to obtain a complete series from 

 elongated to rounded bulbs, but by comparison of wild forms 



" Kerner and Oliver, Nat. Hist, of Plants, Eng^l. Transl., Vol. I., p. 770, 

 and Scott and Sarg-ant, Development of Arum maculatiim from the seed, 

 Ann. Bot., 1898, p. 399. 



t Sachs, Ibid., p. 62. 



J Areschoug-, Bietrag-e Biol. d. Geophilen pflanzen, Lunds Universitets 

 A'rs-skrift, 1895, XXXI,, p. 107 ; Rimbach, Das Tiefenwachstum der 

 Rhizome, Bietrag-e z. Wiss. Bot., 1898, p. 177; and Oliver, Depth in the 

 Soil at which Plants Occur, Journ. Roy. Hort. Soc, 1898, p. 486. 

 1904 March i. f 



