FURTHER STUDIES OF YUCCAS. 185 



as in aloi folia, and similarly reflexed. When fully grown, 

 but not ripe, the fruit is of a clear apple-green color. 



Y. SCHOTTII, Engelm. ( Y. macrocarpa, Engelin.) (PI. 

 3). Though Y. macrocarpa , which appears to be only 

 this species, is not uncommon in parts of southern Arizona, 

 no observations have been made on its pollination, and I 

 was unable to find it in bloom. Flowers collected in the 

 Santa Kita Mountains, July 9, 1881, and in the Huachuca 

 Mountains in September, 1882, show either an unusual dura- 

 tion of the flowering period, or great variability in it. 

 Y. elata and Y. baccata, which are spring-blooming species 

 of the same region, are pollinated by Pronuba yuccasella, 

 which can scarcely be expected to occur as late as the dates 

 mentioned; but baccata, in different localities, is known to 

 have a prolonged period of blossoming comparable with 

 that of the different forms of filamentosa in the southeast, 

 so that it is possible that in its pollination arrangements 

 Schottii bears the same relation to baccata that the autum- 

 nal gloriosa does to filamentosa . 



Y. TRECULEANA, Carr. (PI. 18). This Texan and 

 Mexican species is believed by Riley to be pollinated by a 

 probably distinct Pronuba,* but no observations have been 

 made on it. A specimen which bloomed in the Garden this 

 season was quite as sterile as other cultivated Yuccas aside 

 from filamentosa and glauca, which are pollinated by 

 P. yuccasella, and the aloifolia noted above; and this 

 has been the case on the several occasions when the speci- 

 men has bloomed in the past. 



According to Engelmann f Treculeana is reported by 

 Lindheimer as sterile in Texan gardens, though the wild 

 plants are abundantly fertile. 



Y. BACCATA, Torr. (PI. 20). With the possible exception 

 of Y. glauca, this is the most widely distributed of 

 our species, ranging in a variety of forms from southern 

 Colorado into Mexico and to California, where it extends 



* I.e. 122; Proc. Biol. Soc. Washn. vii. 96; Insect Life, iv. 371. 

 t Collected Writings, 284. 



