Observations on the Fertilization of Yucca, and on Structural and Anatomical Peculiarities in Pro-nuba and Prodoxus.*.

This paper records some recent experiments and observations which establish, fully and conclusively, the fact that Pronuba is necessary to the fertilization of the capsular Yuccas. It describes for the first time how the pollen is gathered and collected by the female Pronuba. The act is as deliberate and wonderful as that of pollination. Going to the top of the stamens she stretches her tentacles to the utmost on the opposite side of the anther, presses the head down upon the pollen, and scrapes it together by a horizontal motion of her maxillae. The head is then raised and the front legs are used to shape the grains into a pellet, the tentacles coiling and uncoiling meanwhile. She thus goes from one anther to another until she has a sufficiency. My observations confirm the accuracy of Dr. Geo. Engelmann's conclusion as to the impotence of the stigmatic apices in some of the Yuccas, and shows how the apparently contradictory experience of Mr. Meehan can be reconciled on variation in this respect in the species of the same genus.

The exceptional self-fertilization in Yucca aloifolia - the only species in which it is recorded - is shown to be due to the fact that in the fruit of this species there is no style, the stgma being sessile, and the nectar abundant, filling and even bulging out of the shallow opening or tube. The flowers are always pendulous, and the pollen falling from the anthers can, under favorable circumstances, readily lodge on the nectar.

*Abstract of a paper read at the Montreal meeting of the A. A. A. S.

The irregularity in the fruit of the Yuccas - considered a characteristic by botanists - is proved by experiment to be due to the punctures of Pronuba.

The egg of Pronuba, which averages 1.5 mm. long, having a swollen apical end, and a long and variable pedicel, is passed into the ovarian cavity of the fruit. The puncture is made usually just below the middle of the pistil, on the deeper depression which marks the true dissepiment, or through the thinnest part of the wall. The horny part of the ovipositor reaches the longitudinal cavity at the external base of the ovule, near the ferniculus, without, as a rule, penetrating or touching the ovule itself, and the dedicate and extensile . oviduct then conveys the egg for some distance (the length of six or eight seeds), along the cavity, the terminal portion of the oviduct being furnished with retrorse hairs which help to hold it in place durine: the act.

The paper concludes with some studies of the internal anatomy of Pronuba and Prodoxus.

[It is proper to say that Mr. Meehan never attempted to controvert Prof. Riley's observations. Mr. M. simply showed that what Prof Riley had found true in Yucca filamentosa, did not occur and was not necessary in Yucca angusti-folia, Unless it was assumed that what was true of one species ought to be true of all, there was nothing to reconcile. Mr. Meehan's observations were accurate in every particular, and exhibition of specimens to sustain his facts were made to the American Association in several successive years. Ed, G. M.]