148 The Botanical Gazette. 
Dr. WILLIAM TRELEASE, although fully occupied by the caresolat 
directorship of the Missouri Botanical Garden, finds time to publi 
periodically, and the periods are getting shorter, pieces of work that 
serve well to continue the reputation that Dr. Englemann brought to% 
Louis. We have before us his further studies upon that f scini i 
subject, the pollination of Yuccas. Dr. Trelease has had further oF 
portunity of studying Yuccas in the field and has added a largeamou® 
of valuable information concerning this interesting group. * 
species of Pronuba are now known to act as pollinators, and it 1s pe 
dicted that others will be found. After giving detailed notes of 
various species, the author gives an interesting discussion adhd: 
probable former range of Yucca and its adaptation to Pronuba polite 
tion. It seems to be fairly well made out that the genus was formeny? 
much wider and more northern range, has been driven southward, we 
is now preserved in favoring localities. It also seems asa 
probable that ancestral forms had separate spreading stigmatic ®” 
which by their union have formed “the peculiar stigmatic © 
into which the pollen must be thrust in order to properly deve 
tubes and fertilize the ovules.” The separation of these st" 
lobes has been observed both in Hesperoyucca and the true Yoee 
A very interesting biological fact is, that a variety of y.W ; 
graminifolia Wood) has as its pollinator a black variety (described? e 
as new) of the Spotted Pronuba which pollinates the speci® 
suggestive fact is that Pronuba yuccasella accompanies the true ¥ 
across the continent, and in California pollinates Y.- baccata, and 
same time is associated with three other forms which are po"™" 
Pacific types. Twenty-three excellent plates illustrate the 
showing various species of Yucca, and Pronuba with di 
Mr. Cuartes Ropertson, whose studies on the relation of 
and insects are well known to the readers of the BoTaNIcar 
has just distributed the results of his studies among the: he f 
he group is one of special interest in this connection, and site! F 
senting details of observations Mr. Robertson discusses the 
to its flower forms, pointing out the least and most SP 
and their probable origin. The unremitting attention 
Robertson has given to this work has brought together ae : 
facts, which will presently represent all of our entomophilows 
*Trevease, Witttam.—Further studies of Yuccas and their 
From 4th annual report of Mo. Bot. Garden. pp. 181-226, plates 23- 
2 Rosertson, Cuaries.—Flowers and Insects—Labiate. Tra 
Acad. Sci. vi. 101-131, 
