INDEX TO AMERICAN BOTANICAL LITERATURE 165 
Whitaker, E. S. Root hairs and secondary thickening in the 
Compositae. Bot. Gaz. 76: 30-59. pl. 1-5 +f. 1-6. 15S 
1923. 
Williams, R.S. Pilotrichum Leoni, sp. nov. Bryologist 26: 50, 
Rif 3-7. 7 30 152% 
A new species of moss from Cuba. 
Williams, R.S. Syrrhepodon parasiticus (Sw.) Besch. in Florida. 
Bryologist 26: 46. f. 7-9. 300 1923. 
Willis, J.C. The origin of species by large, rather than by grad- 
ual change, and by Guppy’s method of differentiation. Ann. 
Bot. 37: 605-628. O 1923. 
Wolf, F. A. Studies of the physiology of some plant pathogenic 
bacteria—VII. Phytopathology 13: 381-384. 18S 1923. 
Wurdack, M. E. Chemical composition of the walls of certain 
Algae. Ohio Jour. Sci. 23: 181-191. O 1923. 
Youngken, H. W. Studies on the greater yam (Dioscorea alata 
Am. Jour. Pharm. 95: 678-684. f. 1-4. S 1923. 
