ENGELMANN — NOTES ON THE GENUS YUCCA. 29 



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Of the baccate Yuccas, T. gloriosa and its allies seem to bear 

 fruit very rarely, as neither my correspondents nor I myself have 

 thus far ever been able to obtain one ; T. Treculiana is abun- 

 dantly fertile in its native localities, but will not fructify, as Mr. 

 Lindheimer informs me, in the gardens of the same region ; T. 

 aloifolia^ however, matures its pods more readily than any other 

 species in Europe, where our moth cannot have an agency in it. 

 We, therefore, are forced to assume that some other mode of 

 fecundation, or even self-fertilization, can take place with them. 

 Occasionally, no doubt, the moth performs its functions in the 

 flowers of this species as well as in the capsular Yuccas. Dr. 

 Mellichamp has found its larvae tunneling the seed rows of 2' 

 aloifolia^ destroying lo to 14 seeds during its growth, and event- 

 ually emerging through the characteristic perforations of the sur- 

 face. He discovered also another larva in the green pods of this 

 species, the egg of which is evidently deposited into the rind of 

 the ovary or young fruit, and which principally feeds on the im- 

 mature pulp and only rarely attacks the growing seed. This, Mr. 

 Riley thinks, must be the larva of a hymenopterous insect, which 

 has, perhaps, nothing to do with the fecundation of the flower. 

 But how may these Yuccas be fertilized without the action of the 

 Pronuba? Probably, occasionally, and, so to speak, accidentally by 

 other insects, or possibly sometimes by the withering and conniv- 

 ing segments of the flower bringing adhering clumps of pollen in 

 contact with the stigmatic juices in the open tube. Such chances, 

 however, seem to be slim, not to say improbable, and in this case 

 impregnation would have to take place on the day following the 

 opening of the flower. 



It has been stated above that the quantity of pollen is small, 

 and that the grains are large and somewhat viscid ; thus, when 

 expelled from the contracting anthers, they remain in little clumps 

 here and there within the flowers, on the papillose filaments, or, 

 more frequently, attached to the inner surface of the perigon. 

 When introduced into the stigmatic tube and in contact with its 

 secretion, its tubes are developed, and, when we carefully dissect 

 a fertilized ovary, large bundles of straight parallel tubes are 

 found to fill the cells and to find their way, one to almost each 

 ovule. I have followed them, through both openings of the 

 ovule, and found them attached with their enlarged end to the 

 outside of the nucleus, separated from the germinal vesicle by two 



