209 STUDIES IN PLANT REGENERATION 
Experiment 6.—Dahlia root-pieces cut in an exactly similar 
way have practically failed to regenerate. The transverse slices and 
the rind-pieces have developed lateral roots as outgrowths from the 
cambium. Parts from which the rind is lacking have not formed any 
organs. The production of shoot-buds from the rind is to be 
looked for, since it із а normal occurrence in the ради but no in- 
stance has yet been observed. . 
As the next type of root, the fleshy tap roots of several plants 
were used; from these the leaf-bearing portion was removed, and 
the rest planted either as one piece or in sections. 
Experiment 7. — A number of these which gave like results 
may first be mentioned together. Roots of carrots (Daucus Car- 
ota), turnips (Brassica Кара), radishes (Raphanus sativa) and sal- 
sify (Zragopogon porrifolius) all produced secondary roots, as in the 
uninjured condition, but none gave rise to a shoot. The carrots 
and salsify formed calluses at the upper exposed ends, but although 
the carrots resisted decay for over five months, and the others for 
varying lesser periods, no further organ-formation took place. 
Experiment 8.-- Parsnips, however, afforded material for more 
extended experiments. Transverse sections of parsnips of various 
lengths were planted with the upper surface above the sand level. 
Calluses formed in two months’ time on both ends. Shoots, it 
was found, could originate from 
the callus at either end ; but, in 
the majority of cases, the apical 
end,underneath the sand, proved 
to be the surface active in their 
formation. In only six out of- 
twenty cases did parts planted 
in the normal position regener- 
ate shoots from the proximal 
end. One of these produced in 
addition a weak shoot from the 
apical end, and one from a cut 
Fic. 1. Боден section of root of made in removing a side branch 
ны ы из have been re- which the root had possessed. 
Experiment 9.—Similar parts 
were next planted in an inverted position. In this case, the shoots 
