FURTHER STUDIES OF YUCCAS. 225 



certain distance from the top, through the backs of the 

 several carpels (PL 22). The seeds of all of these species 

 are thin and flat and the capsules are erect, so that the 

 adaptation to the scattering of the former, a few at a time, 

 by gusts of wind, is that usual in capsular fruits of this 

 kind. It is interesting to note that Whipplei and its 

 variety, representing the aberrant group of BLesperoyuccas, 

 possess the thin margined seeds of the capsular true 

 Yuccas, but the capsules dehisce to the base In a loculicidal 

 manner, that is, through the false partitions, the tough 

 core-like tissue of which is arranged in a transverse lace- 

 like structure (PL 23). Though dissemination depends 

 on the wind in both cases, the seeds of the capsular true 

 yuccas are lifted out of the pods by the wind dipping 

 into the opened top of the cells, while in Hesperoyucca 

 they are removed by puffs of air entering at the side through 

 the lace work across the deep lateral clefts, in the manner 

 beautifully described for Lilium in an anonymous article in 

 the Bulletin of the Torrey Botanical Club, i. p. 46, and 

 well known in the basket fruits of some Aristolochias, etc. 



EXPLANATION OF PLATES ILLUSTRATING YUCCAS AND THEIR 



POLLINATION. 



Plates 1-2, Y. Guatemalensis, flowering and fruiting plant at the 

 Garden. 



Plate 3, Y. Schottii, near Benson, Arizona. 



Plate 4, T. australis, near Sierra Blanca, Texas. 



Plate 5, F. australis, — a specimen from the same region, cultivated at 

 the Garden. 



Plates 6-9, Y. brevifolia, about Hesperia, California. 



Plate 10, Y. data, near Benson, Arizona. 



Plate 15, Y. elata, descending axis, two and a half years from the seed, 

 one-half size, — the principal growth made in the season when figured, 

 (after Engelmann). — Y.filamentosa, germination, X2. 



Plate 16, Hesperoyucca Whipplei, at Summit, California. 



Plate 17, H. Whipplei, var. grammifolia, at Arrowhead Springs, Cal. 



Plate 18, Y. aloifolia.— I, Flower, natural size; 2, pistil and stamens, 

 X 2 ; 3, sections of pistil at points marked by dotted lines, X 2 - 

 Y. Treculeana. — i, flower, natural size (after a drawing by Mrs. H. J- 

 Webber) ; 5, pistil and cross sections, X 2 - 



