CIRCUMNUTATION OF SEEDLINGS. CHAP. L 



pressed alternately with greater and less force on them. Thcro 

 must, therefore, have been movement in at least two planes at 

 right angles to one another. These radicles were so delicate that 

 they rarely had the power to sweep the glasses quite clean. One 

 of them had developed some lateral or secondary rootlets, which 

 projected a few degrees beneath the horizon ; and it is an im- 

 portant fact that three of them left distinctly serpentine tracks 

 on the smoked surface, showing beyond doubt that they had 

 circumnutated like the main or primary radicle. But the 

 tracks were st> slight that they could not be traced and copied 

 after the smoked surface had been varnished. 



Hypicotyl. A seed lying on damp sand was firmly fixed by 

 two crossed wires and by its own growing radicle. The cotyle- 

 dons were still enclosed within the seed-coats; and the short 

 hypocotyl, between the summit of 

 the radicle and the cotyledons, 

 was as yet only slightly arched. A 

 filament ('85 of inch in length) 



f' ^- was attached at an angle of 35 



I ^^ above the horizon to the side of 



J \^ the arch adjoining the cotyle- 



dons. This part would ultimately 

 form the upper end of the hypo- 

 cotyl, after it had grown straight 

 and vertical. Had the seed been 

 properly planted, the hypocotyl at 

 this stage of growth would have 

 been deeply buried beneath the 

 surface. The course followed by 



ifera : circumnuta- 

 tion of straight and verti- 



cal hypocotyl, with filament in Fig. 28. The chief lines of 



fastened transversely across movement from left to right in the 



its upper end, traced in dark- figure wero para ll e l to the plane 



from 830 A iT'lo" {fso^M* ^ * ne ^ wo un ited cotyledons and 



The movement ..f the terminal of the flattened seed; ard this 



bead originally magnified movement would aid in dragging 

 about 18 times, here only 41 



jSIl are held down by a special struc- 



ture hereafter to be described. The movement at right angles 

 to the above lines was due to the arched hypocotyl becoming 

 more arched as it increased in height. The foregoing observa- 

 tions apply to the leg of the arch next to the cotyledons, but 



