1923] 



BEALS — REGENERATIVE PHENOMENA IN PLANTS 375 



differentiated group of meristem cells within the section of the 

 radish. The origin of these cells is not shown, but it is plain 

 that it cannot be from the epidermis or cortical layer, since these 

 layers completely enclose the regenerating tissues; 6 shows a 

 similar group of regenerating cells with a direct connection to the 

 cambium of the root. Since, then, this group shows this con- 

 nection, it seems that its origin must be from those cells or the 

 cambium, c shows the bud enclosed in a similar manner. Other 

 slides exhibited buds likewise enclosed by the epidermis and 

 cortex and with a direct connection to the cambium. Hence, 

 shoots, too, must originate from the division of cambium cells. 



Sections through the vegetative points of the Bryophyllum 

 leaf are shown in pi. 18 : a represents a section through a normal 

 portion showing a vein; b is an enlarged section of the vein with 

 the division of the small phloem cells; c shows that division 

 carried still farther until it disfigures the leaf by a tiny swelling, 

 which results, as in d, in the formation of a regenerated root and 

 shoot. Thus the root and shoot arise from the division of the 

 small phloem cells of the vein near the vegetative points or notches 

 of the leaf. 



i 



General Results 



After about 5 or 10 days, there appeared roots and shoots on 

 the horseradish, parsnip, and sweet-potato in the sterile sand 

 cultures. Buds appeared after 10 days on the radish and potato 

 cuttings which were first washed in Javelle water. Similar 

 results were noted in the water cultures and sand cultures. After 

 the cotyledons of the flax seedlings had been removed, there 

 appeared tiny buds of shoots on the stem, and when the roots 

 had been removed new roots were regenerated (pi. 15). Every 

 notch of the Bryophyllum leaves regenerated new roots and 

 shoots. The tobacco cuttings failed to regenerate and decayed. 

 It was difficult to render them sterile on account of the many 

 hairs on the surface. Freehand sections were made of the parsnip, 

 horseradish, and sweet potato, and stained with iodine. It was 

 plainly evident that the regenerated part was connected with the 

 cambium, the cells of which took on the characteristic color of 



