48 The Ohio Naturalist. [Vol. VII, No. 3, 



Explanation of Plate IV. 



The figures were drawn with the aid of an Abbe camera 

 lucida. Figure 1 was drawn with the Zeiss IS ocular and Leitz 

 1-16 objective; the others with Zeiss 18 ocular and Zeiss 8.0 ob- 

 jective. 



Fig. 1. A single bivalent chromosome from the reduction cell in the 

 ovule of Liliuni philadelphicum. 



Fig. 2. Nucleus from two-celled sac of L. philadelphicum showing 

 expansion of the cytoplasm. 



Fig. 3. Microsporocytes of Marsilea quadrifolia showing centrifugal 

 arrangement of the chromatin in synizesis. 



Fig. 4. Microsporocyte tissue of Marsilea quadrifolia showing sym- 

 metrical synizesis. 



Figs. 5 and 6. Cell rows from opposite sides of sections of Alliuin 

 cepa showing the nature of artificial contraction. 



Figs. 7 and 8. Microsporocytes of Sagittaria latifolia with nucleoli 

 on one side of the contracted chromatin. 



Fig. 9. Microsporocyte of Erythronium americanum showing cen- 

 tral contraction of the chromatin around the nucleolus. 



Figs. 10 and 1 1 . Microsporocytes of Lilium tigrinum showing the in- 

 dependent contraction of the chromatin, the nucleoli being entirely dis- 

 tinct in the nuclear cavitv. 



WEATHER AND CROP YIELD.* 



J. Warren Smith, Section Director, Weather Bureau. 



I am convinced that the yield of most of our staple crops is 

 affected greatly by favorable or unfavorable weather conditions 

 during a comparatively short period of their growth. 



Also that the yield can be very closely approximated at the 

 close of this critical period by an exhaustive study of the weather 

 conditions and crop yields of previous years. 



The United States Weather Bureau is accumulating a vast 

 amount of weather data that are being splendidly tabulated for 

 use in studies of this character and considerable attention is 

 being given to the subject. 



In 1902 Professor W. D. Gibbs and myself charted some very 

 interesting curves showing the relation between the yield of 

 corn in the eight great corn producing states in this country, 

 and the rainfall during June, July and August. 



The period covered was from 1888 to 1902, and the states 

 con.sidered were Ohio, Indiana, Illinois, Iowa, Nebraska, Kansas, 

 Missouri, and Kentucky. 



The result showed that the yield was very little affected by 

 the rainfall in August and not greatly affected by the rainfall 

 during June. The curves, showed, however, that the rainfall in 

 July controls the corn yield to a marked extent. 



* Read at the meeting of the Ohio State Academy of Science. 



