Pollination of Yucca whipplei. 43 



So far as they go, Mr. Coquillett's observations on the actions 

 of Pronuba maculata agree very well with those of Professor 

 William Trelease, who made a special trip through the south- 

 west in the spring of 1892 with a view of studying the pollina- 

 tion of those Yuccas which had not hitherto been studied in this 

 connection. lie has published a most interesting article in the 

 Fourth Annual Report of the Missouri Botanical Garden, en- 

 titled " Further Studies of Yuccas and their Pollination." This 

 is, in fact, a most valuable contribution to our knowledge of the 

 subject, and is complementary and additional to my own paper 

 published in the annual report of the same series for the previous 

 year. Mr. Trelease's life studies of Y. whipplei have added mate- 

 rially to our understanding of its floral characteristics. The 

 anther cells on dehiscing contract so as to expose the pollen 

 freely, but the contents of each cell forms a " rather consistent, 

 two-lobed moist mass, which is held by its lower part but pro- 

 trudes prominently from the open anther." The ovary is free 

 from the longitudinal depressions which in the other Yuccas 

 usually correspond with the appressed stamens. The capitate 

 stigma is slightly indented at the center " and covered with long, 

 hyaline, delicate papilla) which are always moist with abundant 

 secretion that at length becomes almost gelatinous over the 

 middle of the stigma." He found the nectar apparatus well 

 developed, the septal glands, though narrow, reaching commonly 

 to the base of the ovary, with a conducting groove of correspond- 

 ing size. The glands are, also, though smaller, more active than 

 in most other species of Yucca studied by him. Professor Tre- 

 lease also notes that the characteristics of this flower would seem 

 to make it easily self-fertilizable, and remarks on the exceptional 

 occurrence in the lower part of the Cajon Pass of a few plants 

 with more or less abundant, partly developed, but unusually 

 diminutive capsules, in which no evidences of Pronuba action 

 were to be found ; and this, added to the experiment made 

 by Mr. Coquillett, would seem to indicate that where Pronuba 

 is absent whipplei has the same exceptionally limited power of 

 fructification, whether by self-pollination or pollination by other 

 agents, that we know to be possessed by aloifolia among the true 

 Yuccas. Recognizing this possibility, Professor Trelease was 

 somewhat surprised to find that, with the single exception which 

 he noted, no fruit, among all his observations, was discovered 

 which did not clearly show the work of Pronuba. 



