1 



[Annals N. Y. A. S., XL, No. 4, pp. 45 to 54, March 30, 1898.] 



.v/ 



ON HYPERTROPHIED SCALE-LEAVES IN PINUS 



PONDEROSA. 



Francis E. Lloyd. 



(Read Januaiy lo, 1898.) 



[Plate L] 



Early in 1896 the writer was engaged in the study of pollen 

 development and, in order to supply himself with materials, 

 broke off a number of young staminate shoots from a specimen 

 of Pinus ponder osa, the Bull Pine or Yellow Pine of the West. 

 An examination of the same tree in the autumn discovered that 

 the pruning of these large, rapidly growing shoots had resulted 

 in the growth of one to three lateral shoots, a little distance be- 

 low the break. These lateral shoots which were developed from 

 the axils of scales on the upper portion of the shoot of the pre- 

 vious year were sterile, but differed in a remarkable degree from 

 the normal foliage shoots. In the latter the leaves are borne in 

 groups of threes (fascicles) upon very short branches which 

 spring from the axils of small triangular scales which are to be 

 regarded as reduced leaves. In the shoots induced by pruning, 

 however, these scales have been greatly developed, so much so, 

 indeed, as to have become leaves, both in structure and function, 

 while the fascicles, so called, were in most cases not developed 

 at all. When they were developed, however, there was pro- 

 duced the phenomenon of a twig with foliage leaves of two dis- 

 tinct kinds. The same operation was carried on in the spring 

 of the following year (1897) which resulted , similarly. In one 

 case, however, a staminate shoot was produced. 



It has been commonly observed, and was pointed out by 

 Masters^ in 1880, that upon the Juniper, especially upon young 



1 Nature, XXIII : 267. 1880. 



(45) 



