52 



were not able to produce a good yield of corn even if they did start off well, 

 as the next slide will illustrate. 



The black represents the percentage increase of strong plants due to the 

 use of clean, vigorous seed about fifty-five per cent in the first planting, 

 the same the second and third. In the last planting, owing to the warm, 

 moist weather condition during August and September (which was respon- 

 sible for so much of the ear rots this year) you will note that the corn 

 grown from the infected seed did not mature and was much more susceptible 

 to ear rots. As a result the corn grown from good seed gave an increase of 

 79.8 per cent of sound corn. 



This graph emphasizes the same thing. It shows the reduction in per- 

 centage of sound ears in the last planting of corn grown from infected seed. 

 Corn grown from disease-free seed (indicating) is not nearly so susceptible 

 to changes' in environment. On the other hand corn grown from diseased 

 seed is very susceptible to unfavorable conditions. 



The disease-free (indicating on the next slide) has about the same 

 amount of rotten corn for the different times of planting, but notice the in- 

 fluence of time of planting on the amount of rotten corn where diseased seed 

 was used. In the first planting there is thirty per cent rotten corn; in the 

 second, thirty-four; and in the third, fifty. Dr. Hottes will emphasize the 

 importance of some of the physiologic factors about which I have hinted. 



During the display of the following slides I would like to emphasize 

 some of the important genetic factors about which Mr. Mann spoke. The 

 ordinary commercial field of corn is a mixture a conglomeration, if you 

 please of a great number of types, some of which are desirable, but most 

 of which are undesirable. I don't know how to explain this situation to you 

 better than by giving an analogy in livestock. If two breds of hogs, for in- 

 stance the Duroc-Jerseys and Poland-Chinas were turned into the woods and 

 allowed to breed for a few years, after which Chester-Whites, Hampshires, 

 and all the other swine breeds were included, there would be a thorough mix- 

 ture after a few years. A somewhat similar condition exists in the average 

 commercial corn field which contains literally hundreds of different types. 

 When these different types are separated we find that they have distinct 

 individualities. Some of the types, on account of an inherently weak or in- 

 efficient root system, always wilt the first hot day in July. Such a condition 

 is inherited from year to year. It is something with which every farmer 

 is familiar. Many farmers call them (indicating) the "white flags" as they 

 go along the roads in August. 



Frequently, the inherent weakness of the corn is more responsible than 

 the dry weather for the resulting injury to the crop. We need corn that will 

 not be affected by every unfavorable weather condition that obtains. 



Another bad feature about some of these different types is their inabil- 

 ity to stand up (indicating). You can always be sure to find the plants 

 flat on the ground after the first rain and wind storm. Here (indicating) 

 is a plat grown from another pure (homozygous) strain, planted side by 

 side with this one (indicating) only two rows away planted the same 

 time, no difference in soil treatment, wind and rain. You note that it is 

 standing up absolutely straight while the other is leaning badly. This has 

 happened consistently for the last four years. 



This (indicating) is an inbred strain we found to be comparatively re- 

 sistant to the different root and stalk rot diseases with practically no smut 

 or rust. The leaves are deep green in color and free from spottings and 

 streakings. It has a very strong and efficient root system. When two par- 

 ticular strains of this character are combined we get what you see here 

 (indicating). 



In this case (indicating) we have two very undesirable characters com- 

 bined. When this corn first came up there was a full stand until the plants 

 attained a height of six inches. Gradually, however, many of the plants 

 began to wilt and die off. Later they fell over. 



