Ovipositio)! of Pronvha. 



89 



in diameter, tapering at the base and enlarging slightly toward 

 the capitate end, which has also a slightly indurated point. It 

 is inij)ossil)le to follow it with the unaided eye or in fact with an 

 ordinary lens, even if the pistil be at once plucked and dissected ; 

 l)ut by means of careful microscopic sections we may trace its 

 course. From the position assumed by the moth, the ovipositor 

 punctures the ])istil somewhat obliquely, l^ut as the egg is much 

 longer than the diameter of the ovarian cell, the delicate oviduct 

 of the niotli l>ends and then runs vertically along the inner i)art 

 of the cell next the placenta, and leaves the egg extending in 

 tliis longitudinal direction along some seven or eight ovules, as 

 shown in the illustrations (Fig. o, c, c). The apical end of the 



Fig. .").— a, longitudinal section of pistil of Yucca Jilamentosa, showing {b, h) punctures 

 of Pronuba, and (c, c) the, normal position of her eggs in the ovarian cell : d, section of a 

 punctured carpel 7 days after oviposition, showing the egg yet unhatched and the man- 

 ner in whicli the ovules in the neigliborhood of puncture have been arrested in develop- 

 ment so as to cause Che constriction ; e, .section of an older carpel, .showing the larva aliove 

 the original puncture ; /, a seed 13 days from oviiicisition. showing young larv.-i at funic- 

 ular base — enlargements indicated. 



egg soon enlarges (Fig. 1, n), and the embryo may be seen de- 

 veloping in it very much as in the case of the similarly elongate 

 eggs of gall-flies (Cynipidie), though the i)edicel does not shorten, 

 as observed in these last. Segmentation is noticeable on tlic 

 second day. and the Yucca ovule at once begins to swell and 

 enlarge, the irritation (doubtless meclianical) influencing the 

 plant tissue much as in the case of the punctures of the gall-flies 



IJ— Hioi.. Sue., Wash., Vm.. VTI. 1S92. 



