189o.] Botany. 961 
added the Mexican. The richest region in species is probably that 
extending from Washington southward along the coast, thence westward 
to Southern California. 
13. The Migration of Weeds, by B. D. Hatsrep; giving examples 
of the travels of some of the more common weeds of the country. 
14. The Geographical Distribution of North American Grasses, by 
W. J. Bear. Of the 298 genera of grasses we have 115, with 25 more 
introduced. Of the 3200 species in the world we have 850 natives, 
and 125 more introduced, making 975 in all, or considerably more 
than one-fourth of the whole. Bouteloua is represented by all its 
species (27), as is the case also with a number of smaller genera, many 
of which are peculiar to North America. 
15. The Geographical Distribution of North American Cornacez, 
by J. M. Coutrer. Of the three genera Garrya is peculiarly an 
American genus ; its species are mainly Mexican, extending into the 
Pacific region. Nyssa is eastern. Cornus is doubtless of northern 
origin, which hàs, while moving southward, been separated by the Great 
Plains into a western and an eastern group. 
16. The General Distribution of North American Plants, by N. L. 
Bnrrrox. The author divided the North American flora into a north- 
ern (British America, the Sierras, the Rocky Mountains, and the 
Alleghanies) and a southern region (Atlantic Coast, Mississippi Val- 
ley, and a part of California). Referring to the influence of the 
glacial climate, he pointed out many difficulties in the usual method of 
accounting for the present northern flora. 
The Work of the Botanical Division of the Department of 
Agriculture, by F. V. Covite. Two main lines of work have been 
undertaken, viz. : (1) the study of economic problems, especially those 
relating to grasses and forage plants ; and (2) systematic work upon 
.the flora of the country. Publications in two series (economic and 
scientific) are made from time to time. 
of structure of the root-system of the cypress (Taxodium distichum) 
of the Southern States. Several methods of the formation of knees 
were fully illustrated and discussed. The conclusion was that the 
cause of their formation is physiological and not mechanical. 
19. The Potato Scab, a Bacterial Disease, by L. H. BoLLEY. For 
want of time this paper was read before the Botanical Club, 
