Growth and variation in maize. 101 



All the plants were measxired at intervals of three and one -half 

 da.vs heofinniug on June 11, 1908. It will be noted that this was 

 twenty -three days after the corn had been planted. Circumstances 

 over which we had no control prevented us from beginning the mea- 

 surements earlier. However, with the cool springs of Maine the plants 

 had not advanced very far by that time. The measurements were 

 continued at the t-wäce-a-week intervals until July 27, 1908. At that 

 time the plants had practically completed their growth. Three later 

 measurements of the tassel height were taken viz., on August 3, 

 August 10, and August 24. As may be seen from Fig. 1 there was 

 no increase in the average height after August 3. In fact the later 

 measurements showed a slight decrease in height due to the weathering 

 of the tassel tip. 



There are thus six series of measurements available for discussion. 

 In order to faciHtate reference to these series they have been given 

 the following designations. 



Series A — Leaf height of plants from Row 131. 



Series B — „ „ „ ., ., ., 133. 



Series C — ., „ „ „ „ ,, 101—160. 



Series D — Tassel ,, „ „ „ „131. 



Series E — „ „ ., „ „ „133. 



Series F — „ „ ,, „ „ „ 101—160. 



The measurements in the field were all made by one person 

 (F. M. Surface). The computations have been made at various times 

 and by various people. A number of these were done by Dr. E. P. 

 Humbert during his connection with the laboratory. In nearly all 

 cases the computations have been checked several times, usually by 

 different members of the laboratory staff. 



Part I. 



General Growth Curves. 



The first step in the discussion of the growth data has been to 

 form frequency distributions of the various seines for each date. These 

 frequency distributions are exhibited in tables 25 to 30 (pp. 172 — 183). 

 In making these distributions the measurements have been arranged in 

 gioups of 25 millimeters. As will be seen tliis gives reasonably smooth 

 distributions except that in some of the later distributions there are a 



