ENGELMANN NOTES ON THE GENUS YUCCA. 19 



capsules in our St. Louis gardens ; but I found none in Europe, 

 or almost none, I should say, for in the botanic garden of Venice 

 I gathered the pulpy pods from a large Tucca aloifolia, about 15 

 feet high. This was the only Yucca fruit seen by me in Europe, 

 though I have since learned that in other instances also, though 

 only exceptionally, fruit and good seed have been produced there, 

 principally by this same species, and very rarely by others. 



The question why the flowers should almost invariably fail, had 

 been frequently discussed and various reasons suggested, such as 

 sexual incompleteness of the flowers or impossibility of self-fertili- 

 zation of plants originating from the same stock. 



I had observed that all the Yuccas which came under my notice^ 

 opened their more or less pendulous flowers in the evening, and 

 half closed them during the following day, after which they wither- 

 ed. The anthers were observed to open a little before the flowers 

 did, and to expel a large-grained glutinous pollen, which did not 

 seem to readily find its way to the stigma. And how is the stigma 

 constituted ? The conspicuously papillose termination of the pis- 

 til had always been considered the stigma, but closer examina- 

 tion showed its papillae to be epidermidal appendages, corres- 

 ponding to similar ones on the filaments, and entirely destitute of 

 stigmatic functions ; never did they contribute to the development 

 of a pollen-grain occasionally adhering to them. Dr. Mellichamp's 

 notice of a minute drop of glutinous liquid in the tube formed by 

 the coalesence of the so-called stigmas, led me on to further ex- 

 periments. That tube proved to be the real stigma, exuding 

 stigmatic liquor, and insects (in these night-blooming flowers, of 

 course, nocturnal insects) must be the agents which introduced 

 the pollen into the tube. Last June, several forms of Yucca which 

 were blooming under my windows , were carefully watched, and 

 soon different species of beetles were found in the flowers, but not 

 as regularly and frequently as white moths, which, usually in 

 pairs, disported themselves in the open flowers at dusk, and were 

 found quietly ensconced in them when closed in day-time.* The 

 suspected insects were handed over to my friend, Mr. C. V. Riley ^ 

 who thereupon took up the zoological part of the investigation, 



* These snow-white ''millers" which I have found in almost every flower examined 

 when closed in daytime, doubtless enter their " ivory palaces " at night, and would be quite 

 sufficient for the purpose. Dr. M. — Later, the same correspondent adds : Where I have 

 found many moths last year, I noticed none or few this season. A few weeks later the plants 

 were found without fruit, or with fruit bearing empty seeds. 



