214 



THE GARDENER'S MONTHLY 



[July, 



kinds of ferns. If not wanted in the summer, 

 they could be set away in some dry place until 

 autumn. Most of them are easily cultivated, 

 and their novel and curious variety would make 

 them objects of great interest. 



ON THE FERTILIZATION OF YUCCA. 



Read before the American Association for the Advancenieut of 



Science, at the meeting at Saratoga, by Thomas 



Meehan, Fellow of the Association. 



In the transactions of the Academy of Science 

 of St. Louis of April 15, 1873, our distinguished 

 associate Dr. George Englemann has some 

 "Notes on the genus Yucca," in which occurs 

 the following passage: "The conspicuously pa- 

 pillose termination of the pistil had always been 

 considered the stigma, but closer examination 

 showed its papillae to be epidermal appendages, 

 corresponding to similar ones on the filaments, 

 and entirely destitute of stigmatic function ; 

 never did they contribute to the development of 

 a pollen grain occasionally adhering to them. 

 Dr. Mellichamp's notice of a drop of glutinous 

 liquid in the tube formed by the coalescence of 

 the so-called stigmas led me to further experi- 

 ments. That tube proved to be the real stigma, 

 exuding stigmatic liquor, and insects must be 

 tfte agents which introduced the pollen uito the 

 tube " Subsequent investigations by our es- 

 teemed associate Professor Riley led to the dis- 

 covery of a new genus of Lepidoptera— Pron^fta 

 yuccasella — and which has proved to be the insect 

 agent which fertilizes the flower. In the same 

 number of the Proceedings, Professor Riley de- 

 scribes this insect and says, " with her maxilary 

 tentacle, so wonderfully modified for the pur- 

 pose, she collects the pollen in large pellets, and 

 holds it under the neck and against the front 

 trochanters. In this manner she sometimes car- 

 ries a mass twice the size of her head. Thus 

 laden she clings to the top of the pistil, bends 

 her head, thrusts her tongue into the stigmatic 

 nectary and brings the pollen masses right over 

 its mouth. In this position she works with a 

 vigor that would indicate combined pleasure and 

 purpose — moving her head and body from side 

 to side, and apparently making every effort to 

 force the pollen into the tube. Such is the 

 method by which our yuccas are fertilized." 



It may be remembered that at our meeting at 

 Buffalo I produced three capsules that had not 

 been produced bj' this elaborate process, but 

 simply by mere touching of the papillose apex 



with one of the flower's own polleniferous 

 anthers. Professor Riley was so sure that the 

 seed-vessels could not have been produced in 

 that way ; that there must have been some insect 

 j agency unknown to me in addition to my work, 

 I that at the conclusion of my paper he asked per- 

 mission to cut open the capsules, sure of being 

 able to show the larvae in the fruit; but he found 

 them not. I recall these matters to show that I 

 have not misapprehended the position our friends 

 take on this question. 



I now again exhibit numerous seed vessels 

 from this plant of Yucca angustifolia in which no 

 i trace of larvae can be found; and seed vessels of 

 Yucca filamentosa growing but a few yards from 

 the other, which are infested by the Pronuba 

 yuccasella, as this species always is when it seeds 

 at all. 



The history of the fruiting- of the Yucca anguS' 

 tifolia is as follows : It flowered in 1875, but pro- 

 duced no fruit.* In 1876 the early flowers prov- 

 ing infertile, I applied the flower's own pollen to 

 the apex of the pistil of the four last flowers that 

 opened ; these produced the four capsules exam- 

 ined by Professor Riley as already noticed. In 

 1877, noticing that the Pronuba abounded in the 

 flowers, no hand application was made, and 

 there was no fruit. In 1878 the flowers were 

 again left to the insects with no fruitful results. 

 The past season pollenization by hand was re- 

 sorted to, and the numerous seed vessels I exhibit 

 ! followed. As the pollen was merely applied to 

 i the papillose apex it shows that in this species 

 the elaborate and wonderful ingenuity of the 

 insect in applying pollen as described by our 

 friend is wholly unnecessary. 



We now come to some extremely interesting 

 considerations, growing out of these facts. 



Pronuba yuccasella, the yucca moth, has for 

 years abounded on my flowers of tVie Yucca 

 [filamentosa. It has not been known to visit any 

 other plant than yucca. Yucca angustifolia 

 begins to flower from two to three weeks, and its 

 blossoming is all over before Yucca filamentosa 



* At the conclusion of this address, delivered at the Saratoga 

 meeting of the American Association, Prof. C. V. Riley made 

 some remarlis which unfortunately I did not hear. The news- 

 paper reports make him say that I was mistaken in the insect I 



1 found in Yucca angustifolia, that it was not Pronuba yuccasella. 

 1 have called Prof. Riley's attention to this, and have asked for 



; a correct note of what he did say, but have only the reply that 

 he is " not answerable to a newspaper report.'' It remains 

 then only for me to say in reply to the " newspaper report '' 

 that at the outset of my observations on Yucca angustifo,Ua,l sent 

 one of the insects caught to Professor Riley asking: "Is this 

 certainly Pronuba uccacella ?" and he replied that it was 



