Apr. 15-Sept. IS, 1919 



Illustrations vn 



Relation ok Weather to Fruitfxjuness in the Plum 



Page 



Plate 13. Plum tree and fruiting branch showing difference between number 

 of flowers borne and quantity of fruit set: A.— The appearance of a plum 

 tree bearing a normal crop of bloom. B.— A single fruiting branch 2 years 

 old showing the contrast to A 126 



Plate 14. A. — Stigma of Minnesota No. 21, a greenhouse tree, 24 hours after 

 being selfed, showing the condition of papillate cells in the stigma, pollen 

 tubes, and also traces of the stigmatic fluid. B.— Stigma of Minnesota No. 

 35, open to cross pollination, showing the condition of a stigma three days 

 after bloom, having withstood a rain of 0.87 inch which fell in the two days 

 previous, lasting in all 18 hours. C. — The tiurgid papillate cells in Sapa 

 before receptiveness. D. — Opata. Same as C. E. — Abscission layer Min- 

 nesota No. 35, showing the cells of the layer 11 days after bloom. F. — The 

 surface at the abscission layer of Assiniboin after the style has fallen, 12 

 days after bloom 126 



Plate 15. Graphic analysis of the weather from the standpoint of wind, stm- 



shine, rain, and temperature for seven years from 1912 to 1918 126 



Structure op the Maize Ear as Indicated in Zea-Euchlaena Hybrids 



Plate 16. Intermediate stages between a simple spike of the pistillate inflores- 

 cence of Euchlaena and an ear of maize : A. — Spike of pure Florida teosinte. 

 B. — Spike with slightly shortened axis. C. — A still more compact spike 

 with an increased number of seeds. A-C have single spikelets and separate 

 two-ranked alicoles. D. — Spike with single spikelets and yoked alicoles, 

 irregularly fotu-rowed. E. — Compact spike with two-ranked separate 

 alicoles and single spikelets. F. — Spike with paired spikelets and four 

 ranks of yoked alicoles. G. — Transition stage between four-rowed and 

 eight-rowed ear. H. — Ear of maize with eight rather poorly defined rows 

 of seeds 136 



Plate 17. Pistillate inflorescences of hybrid between Euchlaena and maize: 

 A. — Showing pedicelled staminate spikelets with sessile pistillate spikelets. 

 B. — Closely compacted inflorescense with two rows of alicoles and four 

 rows of seeds. C-E. — Spirally twisted inflorescences, with three rows of 

 alicoles 136 



Plate 18. Pistillate inflorescences of hybrid between Euchlaena and maize, 

 showing yoked alicoles: A-C. — The alicoles are in four rows corresponding 

 to an eight-rowed ear. D. — The alicoles are in five rows, corresponding 

 to a ten-rowed ear * 136 



Ultra-Microscopic Examlnation op Disperse Colloids Present in Bitu- 

 minous Road Materials 



Plate 19. A. — Microscope with ray filter and arc lamp for dark field illumina- 

 tion. B. — Photomicrograph of cross-line micrometer scale, showing col- 

 loids in dark field. X320. Taken by E. A. Shuster, jr.. Photographic 

 Laboratory, United States Geological Survey 176 



Effect of Removing the Pulp from Camphor Seed on Germination and 

 Subsequent Growth op the Seedlings 



Plate 20. A camphor seed bed, showing the growth of seedlings from pulped 



and unpulped camphor seed planted in alternate rows 238 



Plate 21. A. — Camphor seedlings at the time of transplanting. B. — Camphor 



seedlings cut back and trimmed ready for transplanting 328 



122502°— 19 7 



