Pomona College Journal of Economic Botany 413 



activity of its crown, but, when an increased production of leaves begins, it 

 broadens gradually in its upper part, till the moment arrives at which the 

 plant reaches and passes the maximum of its vegetative activity. The 

 production of supernumerary leaves now gradually ceases, giving origin to 

 the inverted phenomenon or the tapering of the trunk at its upper end. 

 Such apparently is the process by which we may hold that the production of 

 a fusiform or clavate trunk has been brought about. But the economic or 

 utilitarian side of this contrivance consists, as I believe, in the building of a 

 store house of reserve materials, to be utilized during the reproductive period 

 of the plant, for it seems that the anomalous swelling decreases in size, when 

 the plant begins to bear fruits. In this connection I have to observe that 

 those palms with large and bulky trunks, as Sagus, Jubaea, Washingtonia, 

 etc., have these of a soft pith-like texture in the interior, while their paren- 

 chymatous cells are filled with starch grains, especially in the period preced- 

 ing the first emission of the spadices, that is, at the beginning of the repro- 

 ductive period. We may, therefore, by analogy, suppose that the bulging of 

 the trunk at a determinate period of the life of certain palms, may prove 

 useful to them as magazines of reserve materials which accumulate there 

 during the period of maximum vegetative activity of the plant, to supply the 

 needful nutriment to the reproductive organs when the decrease in that 

 activity shall set in. 



The increase in diameter of the trunk in palms is certainly not a con- 

 stant fact, for very many of them retain a trunk of unvarying thickness 

 throughout their lifetime, as do those of an arundinaceous, calamoid or 

 arecoid (cylindricus — Mohl.) type. But even where a general or local 

 augmentation in thickness does take place, this is not always of the same 

 nature ; different causes must intervene both where there is a general increase 

 throughout the entire trunk as in several palms of the cocoid type {Jubaea, 

 Washingtonia, Livistona, etc.) or where only a bulbiform thickening takes 

 place at the base (as in Acantophoenix crinita, Latania commersonii, 

 H'yoplwrbe commersonii, etc.), or again where the increase is represented by 

 a more or less pronounced partial bulging in the intermediate or upper part, 

 as in Iriartea ventricosa, Acrocomia fusiformis, PritcJuirdia wrightii, 

 HypJiaene venticosa, etc. 



To better explain the difference between these different structures in the 

 trunks of palms, I think that it will not be entirely useless to expound here, 

 very briefly, my conception of the general structure of the trunk of a palm. 



The primx)rdial leaf of a palm, when fully developed and furnished at 

 its base with a primordial root, produces from its axil a second leaf; this in 

 its turn emits a second root which makes its way through the fundamental 

 tissue of the corm-like base of the preceding or firstborn leaf, but externally 

 and above the firstborn root. The progressive evolution of the entire plant 

 is apparently a repetition of this phenomenon, from which it results that 

 the more recently produced roots must be the more external, and that their 



