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THE AMERICAN NATURALIST. [Vol. XXXVII. 



case yet given. The return to a five-lobed leaf, then a three- 

 lobed leaf, and finally to a simple leaf beneath the flower, a con- 

 dition simpler than any seen in the seedling or spring growth as 

 in so many other cases. This species is a good one for studying 

 localized stages as the leaves are much cut up and pass through 

 many, but nevertheless definite, stages. 



Bryophyllum tubiflorum Harv. Figs. 50, 51. 



This plant is known to many by its power of reproducing by 

 buds from the notches of the sides of the leaf. When a leaf is 

 placed on damp sand or earth a bud soon starts out from each 

 of these lateral notches, and young plants result, some showing 

 greater strength than others. The leaf shrivels and finally dries 

 up leaving a ring of new plants. These young 

 plants show localized stages comparable to the 

 seedling. One of the growths from such a 

 leaf bud is shown in Fig. 5 1 . The first pair 

 of leaves are entire, the second have a single 

 notch on each side, the third two on a side 

 and so on. This repetition of characters is 

 a- >>tn nig a- any hvii in early spring growth. 

 J lorum - In the study of localized stages in develop- 



ment, as also noted in the preceding paper, in the study of spring 

 growth the leaves of weaker shoots seem to be better than more 

 vigorous ones for study as they repeat the greatest number of 

 stages and revert to more primitive characters. Not only is this 

 tendency to a repetition of characters found in spring growth 

 from the ground, but also from the stems of the preceding 

 year's growth and even as in the last case noted in growths from 

 the leaves themselves. 



In the leaves of flowering shoots or weak terminal growths at 

 the end of the season the same stages are passed through as in 

 the seedling or spring growth but always in the reverse order of 

 sequence. This which is considered localized senescence is 

 directly comparable to senescence of the whole individual as 

 shown by Prof. Hyatt in his studies of cephalopods. In several 

 cases described it is shown that beneath the flower the leaves 



