274 PROCEEDINGS OF THE ACADEMY OF [1888„ 



CONTRIBUTIONS TO THE LIFE HISTORIES OF PLANTS, NO. II, 

 BY THOMAS MEEHAN. 



The leading tacts, given in these papers, have been communicated: 

 verbally during the year 1888 to the Academy of Natural Sciences 

 of Philadelphia or its Botanical Section. In })reparing them for 

 publication, it was believed they might add to the interest of the meet- 

 ing of the American Association for the Advancement of Science at 

 Cleveland, if read thei-e prior to a full publication here. This state- 

 ment is necessary to explain the somewhat controversial manner, 

 intended to excite debate, in which the facts are presented. The 

 remarks of those who discussed the papers, are briefly given in the 

 Botanical Gazette, for September 1888. 



Some new facts in the life History of Yucca. — In the extremely 

 ftiscinating subject of the relation of insects to flowers no plant 

 possesses a greater interest than the Yucca. It is assumed that in- 

 sects' visits are arranged for cross-fertilization, and this again on the 

 assumption that cross-fertilization must in some way, be a great 

 benefit to the species or to the race. This conclusion is a fair one. 

 Some good has been found from cross-fertilization, and some flowers 

 seem only to produce seed when cross-fertilized -but in Yucca we 

 have the anomaly of a floral structure so arranged that it can scarcely 

 pollinate itself or in any way receive pollen except by artificial aid 

 and yet that arrangement results, in so far as we can see, simply from 

 the use of its own pollen. There is in Yucca a more wonderful rela- 

 tion between the insect and the flower fertilized than possibly in any 

 other case. Professor Kiley, to whom the great credit of this 

 wonderful discovery is mainly if not wholly due, has well expressed 

 this intimate relation in the insects name Prouuba yucco.sella, and 

 yet it is evident to those who observe closely the working of this 

 wonderful arrangement, that it has no relation to cross-fertilization, 

 but results in self-fertilization. In most cases, as clearly shown by 

 the observations of Prof. Kiley, the pistil receives through the medium 

 of the insect the pollen' from its own flower, or at best the pollen 

 from the flowers on the same or adjacent plants; which is equally 

 self-fertilization. Just why this plant should be put to all this 

 trouble to get results through an agent, with no other result than it 

 would obtain if it did the work itself, is surely a problem worthy of 

 any endeavor to solve. ^lankind has servants and slaves, and even 



