THE STEM OK SHOOT. 



119 



fused together to a single apex above. Senebier found 

 the haulms of two distinct grasses united together to 

 form a single stem whose apex bore wheat on one 

 side and rye on the other. 



2. Congenital. — No instance of this kind of union 

 between two or more main shoots appears to be 

 known. 



But it is common between the main shoot and an 

 axillary branch. When this phenomenon occurs, of 

 which instances will now be given, the appearance is 

 presented of an extra-axillary branch ; as it is, how- 

 ever, very rare in Nature, it must always be ascribed 

 to fusion of the two axes and not to displacement of 

 the subsidiary shoot or branch out of its normal 

 position. 



hi Arnpelopsis Veitc-hii a tendril had become split 

 into two ; one of the two branches so formed was 

 carried up, by congenital fusion with the strong axillary 

 shoot, to the next node above, where it left the axis 

 immediately below the leaf of that node. In the 

 sycamore axillary shoots, at intervals along one side 

 of the stem only, were seen fused for a certain height 

 with the main axis. 



A good instance of it has also occurred in the long- 

 rooted cat's-ear (Hypochseris radicata). 



De Vries describes and figures all grades of adnation 

 of this kind in Hj/porhceris glabra, the extreme case 

 being that of complete fusion of both the peduncles 

 and the capitula of the main and axillary shoots. 



Prof. F. W. Oliver informed the writer of a case in 

 a species of Polygonum in which an axillary shoot 

 sprang from the stem close below the node above that 

 to which it belonged ; as it, of course, arose congenitally 

 in that position, the ochrea of the node to which it 

 morphologically belonged was not split on the outer 

 side to admit of the shoot's passage, a fact which, of 

 course, would tend to heighten the illusive appearance 

 of the axillary shoot being displaced and not fused with 

 the main axis. It was interesting to note that the 



