[Vol. 10 



376 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



protoplasm stained with iodine while the surrounding cells were 

 filled with purple-stained starch grains (pi. 15). From the pre- 

 pared sections, it can be seen that, according to pi. 17, the regen- 

 erated parts of the potato and radish came from tissues other than 

 the epidermis or cortex. The one drawing on this plate shows 

 the definite connection with the cambium. The parsnip slides 

 exhibited an exactly similar condition. Regeneration in the 

 Bryophyllum occurs directly from the division of the small 

 phloem cells (pi. 18). The sections of the flax both in cross and 

 long views show the regenerated parts arising from the epidermis 

 cells. First the epidermis divides and then the innermost row of 

 those cells and the stimulated cells of the region just beneath 

 form the regenerated part, root or shoot (pi. 16). 



Conclusions 



Regeneration occurs in the (a) flax stem from the division of 

 the epidermal cells ; (b) Bryophyllum leaf at the notches from the 

 division of the phloem cells of the veins; (c) sweet-potato, horse- 

 radish, and parsnip, from the division of the cambium cells. 



Final Conclusions 



Basing my conclusions on the instances cited in the literature 

 and upon the laboratory experiments, I am convinced that re- 

 generation occurs (1) from cambium cells when they are abund- 

 antly present and fully developed, as in the horseradish, sweet- 

 potato, and parsnip, (2) from the young epidermal cells of seed- 

 lings before the central cylinder has a well-developed cambium, 

 as in the flax seedlings, and (3) from the small and actively divid- 

 ing cells of the phloem, as from the veins of the leaves of 



Bryophyllum. 



Bibliography 



Chamberlain, C. J. ('15). Methods in plant histology. 307 pp. 1915. 



Duggar, B. M. ('20). Hydrogen ion concentration and the composition of nutrient 



solutions in relation to the growth of seed plants. Ann. Mo. Bot. Gard. 7: 



1-49. /. 1-7. 1920. 

 Figdor, W. ('06). Uber Regeneration der Blattspreite bei Scolopendrium Scolo- 



pendrium. Ber. d. deut. bot. Ges. 24: 13-16. pi. 1. 1906. 

 Goebel, K. ('00). Organography of plants, pp. 41-51. 1900. 



