182 MISSOURI BOTANICAL GARDEN. 



nothing definite has been made known concerning either the 

 Pronubas which frequent the several species of Yucca, or 

 their mode of operation, although Riley predicts the prob- 

 able discovery of distinct species of Pronuba for the Mexican 

 Y. Jilifera* and our own Y. rupicolaj Y. Treculeanaj 

 and Y. baccata.% 



The following pages contain the results of a further field 

 study which I have been enabled to make during the spring 

 of 1892, through the interest of the Board of Trustees of 

 the Garden. In bringing the observations together, they 

 have been arranged under the respective species studied, the 

 classification of the latter being substantially that employed 

 in the detail illustrations of the last volume. § 



YUCCA. 



Filaments nearly or quite free from the petals; pollen powdery; style 

 stout, not capitately expanded nor long-papillate, with a rather open stig- 

 raatic axile canal ; fruit baccate, spongy, or capsular with septicidal and 

 apical-loculicidal dehiscence. 



a. sarcoyucca, with flesliy fruits. 



Y. aloifolia, L. (PI. 18).— According to Riley, || in- 

 dividuals of this species which bloom simultaneously with 

 Y. filamentosa along the southeastern coast, are pollinated 

 by Pronuba yuccasella. The species is, however, quite 

 unique in setting good fruit rather abundantly in cultiva- 

 tion when Pronuba does not appear to be present.fl This 

 was the case in the Garden this year, when the species 



* Lc - 121 « t *. c. 122. % Proc. Biol. Soc. Washn. vii. 96. 



§ Third Report Mo. Bot. Garden, 161. || J. c . 121. 



1 The principal references to the fruiting of aloifolia without Pronuba 

 are the following: Deleuil, Rev. Horticole. — abst. in Gard. Chron. 1880, 

 xiii. 807; Engelmann, Gard. Chron. 1872,941, Collected Writings, 284 ; 

 The Garden, fide Vick's Mag. 1880 and Riley in Proc. Amer. Ass. Adv.' 

 Sci. xxix. 624; Gardeners' Chronicle, 1880, xiii. 81; Riley, Third Garden 

 Report, 118 etc.; J. v. V. [van Volxem], Gard. Chron. 1882, xviii. 407. 

 The note of Layard in Nature, xxii. 606, may perhaps refer to this 

 species, though the species is not named. 



