58 BUDS AND STIPULES 



are basifugal (fig. 98), as in the Pea, Ailanthus, Maho- 

 nia, &c. 



A similar difference in the mode of growth may be 

 shown to occur even when there are no leaflets. Thus, 

 Steinheil made a nick with a knife on a young 

 growing leaf of Mesembryanihemwn, half way up, and 

 found that in the full-grown leaf it was much nearer 

 the apex than the base. M. deltoideum has a number 

 of small fleshy points, especially one at the summit, and 

 two at each side. These are in proportion much nearer 



/h 



FIG. 97. To ILLUSTRATE FIG. 98. To ILLUSTRATE 



BASIPETAL GROWTH. BASIFUGAL GROWTH. 



the base in the young than in the full-grown leaf. 

 Again, in Urtica biloba the notch at the apex of the leaf, 

 from which the species takes its name, reaches in the 

 young leaf to the centre, but in the full-grown leaf 

 only a third or a quarter of the length. In pinnate 

 leaves the insertions of the pinnae are, as Steinheil says, 

 marks written by Nature on the leaves, and when, as in 

 many cases, they are nearer together at the base, the 

 upper leaflets are the older and the lower ones younger. 

 Thus, a growing leaf of Asclepias syriaca may have six 



