1920] CHILD &• BELLAMY— BRYOPHYLLUM 2 



55 



Thus far experiments have been made chiefly with three species 

 of plants: Bryophyllum calycinum, in which physiological isolation 

 and outgrowth of buds in the notches of the leaves was brought 

 about by cooling a region of the petiole; seedlings of Phaseolus 

 multijiorus, the scarlet runner bean, in which isolation and out- 

 growth of axillary buds were brought about by cooling a region of 

 the main stem between the buds to be isolated and the chief tip 

 of the plant; Saxijraga sarmentosa, in which the isolation and 

 development of the runner tip into a new plant was brought 

 about by cooling a zone of the runner below its tip. A brief 

 report of the results of these experiments has already appeared 

 (Child and Bellamy 7). The present paper is devoted to the 



experiments on Bryophyllum. 



Experiments 



The individual plants used ranged from o .6 to 1 .3 m. in height. 

 Leaves from the upper half of the plant were selected for experi- 

 ment in nearly all cases, particularly in the larger, older plants, 

 in which the lower leaves are often in poor condition, or, when 

 the plants have been kept in moist air, show more or less outgrowth 

 of the buds during the winter in the intact plants. Various pre- 

 liminary experiments were performed in order to determine to 

 what extent physiological isolation might be brought about by 

 external conditions acting directly on the leaves while still attached 

 to the intact plant. By arranging bowls or jars containing water 

 on ring stands about the plant in such a way that particular leaves 

 were more or less completely submerged, it was found that at 

 least during the winter and early spring months some of the leaf 

 buds would grow in some cases, but to a greater extent on leaves 

 at lower than on those at higher levels of the plant. 



Again, a sudden rise in temperature from 15 to 25 C. in satu- 

 rated atmosphere would usually induce outgrowth of some buds on 

 leaves of the middle and lower levels of the plant, but not on 

 those near the main tip. Such outgrowth usually consisted only 

 of roots, and these were often inhibited after a few days. 



Direct injur}' to the petiole, for example, compression by a 

 screw clamp or by a cut partially through the petiole, was usually 



