412 Pomona College Journal of Economic Botany 



Martius supposes that the peculiar structure of the fusiform or bulging 

 trunkst may have originated in an increased number of leaves thrown out 

 during a period of maximum vegetative activity of the plant, which subse- 

 quently and gradually decreased. This same explanation is accepted by Dr. 

 J. W. Harshberger in his paper on the hour-glass stems of the Bermuda 

 palmetto.}: In this palm the stem frequently exhibits one or more waist-like 

 constrictions, or hour-glass contractions, with interposed swellings, which are 

 produced, according to this observer, by alternating periods of seasons favor- 

 able or prejudicial to the perfect growth of this palmetto. These periods are 

 in direct correspondence with a larger or smaller crown of leaves, the larger 

 diameters of the stem corresponding, of course, to the periods in wliich, as 



.the more numerous leaves show, the vegetative forces are most active. The 

 author adds, also, that "The increase is due to the expansion of the paren- 

 chymatous fundamental tissue, which separates the vascular bundles accom- 

 panied by an increase in the cell-cavity and by the increased thickening of 

 the walls of the sclerenchymatous fibers which support the bundles." 



If w^e take a special case of bulging, that for instance of Pritchardia 

 wrightii, we may imagine that in youth the trunk for a certain time remains 

 more or less cylindrical, probably on account of the uniform vegetative 



iMartius: Hist. nat. Palm., v. Ill, page LXXXIV. 



JProceedings of the Academy of Nat. Sc. of Philadelphia, 1905, page 701. 



