156 



[M. Roland-Gosselin's bold explanation of the occurrence of 

 these Rhipsalis species of Cactaceae in tropical Asia and Africa, 

 the family being otherwise American in distribution, is an 

 important contribution. — N. L. B.] 



A CASE OF ABNORMAL DEVELOPMENT OF A SHORT 

 GROWTH IN PINUS EXCELSA 



By Arthur H. Graves 



The characteristic development in the genus Finns of two 

 sorts of shoot axes — long and short — is well known to all who are 

 acquainted with the genus. The long growth (Langtrieb) is 

 represented by the main axis or axes of the shoot system; the 

 short growths (Kurztriebe) consist of much abbreviated branches 

 which are borne on the long growth, arranged spirally upon it, 

 and subtended by its scale-like leaves. These short growths 

 or branches are characterized primarily by the fascicles of 

 leaves they bear; each one, in the group of the white pines, 

 developing normally five leaves, in a whorl-like cluster or "fas- 

 cicle." Microscopical examination shows near the base of these 

 leaves, and surrounded by them, a tiny growing point at the 

 terminus of the short growth. Under ordinary conditions this 

 growing point never develops further; and at the end of two or 

 two and one half years the whole short growth is shed, in essen- 

 tially the same manner as a leaf is cast from one of our deciduous 

 trees. 



Under special conditions, however, as for example when the 

 growing point of the long growth is injured, a development of a 

 short growth into a long growth rarely occurs.* An interesting 

 case of this kind was recently found by the writer on a tree about 

 15 years old of Pinus excelsa Wall, in the New York Botanical 

 Garden, and is illustrated in figure i. The five leaves com- 

 posing the original fascicle may be seen at the base of the 

 shoot, one of them having been slightly twisted in order to show 



* Engler, A., und K. Prantl. Die natiirlichen Pflanzenfamilien nebst ihren 

 Gattungen und wichtigeren Arten insbesondere den Nutzpflanzen. 2^: 29 note. 

 Leipzig. 1889. 



