340 THE JOURNAL OF INDIAN BOTANY. 



From this we may conclude that neither the stem itself, nor the 

 opposite bud, nor the axillary bud, exert any absolute inhibition, on 

 the development of the marginal notches, and probably affect it very 

 little. 



D. Regeneration in leaves still attached to the living plant. — 

 Several normal, erect, healthy plants of Bryophyllum were found in 

 which roots and shoots had arisen from the notches of several leaves 

 in contact with the parent plant. It should be mentioned that the 

 preceding week had been a very rainy one. Most of the leaves 

 jvhich had grown shoots at their notches were found to be of a 

 slightly paler green colour, but there were also several green leaves 

 among the number. In none of these stems had the terminal buds been 

 injured or destroyed and they were growing quite well. In the case 

 of one plant where the terminal bud, had been accidentally destroyed, 

 the notches in the leaves had not grown out, but the axillary bud 

 lower down, was starting to grow. The stems of all these plants were 

 quite erect and to all appearance normal. There was no indication of 

 their roots having been injured or of any other pathological condition 

 as suggested by Loeb in his objection (5) to Miss Lucy Braun's very 

 similar observation. 



Loeb, indeed contended (l) that "when these leaves are attached 

 to the stem of the whole plant, in the natural condition, they never 

 produce roots and shoots in their notches." The chief factors which 

 he mentions, as tending to prevent the formation of roots and shoots 

 on the leaves when in the natural condition, are (l) the growth of 

 buds on the main stem and (2) root-pressure. His explanation is that 

 the formative materials which are required for active growth, are 

 constantly flowing to the terminal bud from all the other parts of the 

 plant and hence the notches in the leaves have no chance of growing. 

 This explanation does not, however, apply to the instances cited above, 

 as in all those cases, the terminal buds on the main erect stems were 

 quite healthy and active. 



Turning now, to the second factor that Loeb mentions, he says 

 that the presence or growth of roots on the main stem inhibits the 

 growth of notches in the leaves because. of root-pressure. 



It is difficult to conceive how root-pressure can inhibit growth in 

 the notches of the leaf, and Loeb does noc explain how it does. In 

 the concluding passages of his paper (l), he says that attempts to 

 induce growth in the notches of the leaves proved futile. He says 

 " the writer left several leaves of the plant submerged in water for 

 months without any results ", and therefore concludes that root- 

 pressure is the inhibiting factor. 



\yith a view to find out, whether this was really the case, three 



