126 



Pomona College Journal of Economic Botany 



would not find their way into samples of nuts from that source. On the other 

 hand their presence among nuts from B. nobilis is perfectly normal and what 

 would be expected since in this species the opercula fall into the interior of the 

 pyxidia and become mixed with the nuts. Moreover, the opercula, so far as the 

 writer has been able to observe, are always of the B. nobilis type, as shown in the 

 figure. They vary in form from ovoidal bodies to cones of varying slope, being 

 modified apparently by the size and degree of persistence of the columella as well 

 as by the extent of the grinding against surrounding nuts to which they have 

 been subjected during shipment. All, however, are provided with a distinct apical 

 point except where it has been broken off, in which case the fact is usually quite 

 evident. It cannot be denied that the absence of opercula of the B. excelsa type 



Figure 48. Pyxidium of Brazil nut cut open to show structure, with nuts in place. 

 Note the pointed operculum, and the opercular opening becoming very broad 

 toward the interior of the pyxidium. Small specimen, natural size. 



does not preclude the possibility that nuts of this species may be occasionally 

 mixed with those of B. nobilis, since the writer is not aware that it is possible to 

 distinguish the species from the character of the nuts alone. 



(b) Every pyxidium of the Brazil nut which the writer has had an oppor- 

 tunity to examine has indicated that the fruit is that of B. nobilis. Their main 

 points of structure are well shown in the Figures 48 and 49 which illustrate pyxidia 

 obtained from different sources. A comparison of the photographs with Miers' 

 description of B. nobilis will leave no doubt of their identity. Most if not all of 



