p. W. ZIMMERMAN 87 



hazardous to humans. Consequently the use of hormone-Uke herbicides 

 appears to be the most feasible method for controUing water weeds on a 

 large-scale basis. Working with the army engineers during the last two 

 years, Hitchcock, Kirkpatrick, Earle, and I have shown that waterways 

 can be kept free of aquatic weeds by means of 2,4-D sprays and proper 

 maintenance control. The pounds per acre, methods of applying the 

 spray, and weather conditions are all important when the first application 

 is made. Complete eradication may not be possible, but practical patrol 

 maintenance is feasible and keeps weeds within bounds. By means of a 

 helicopter the equivalent of 600 acres per day can be sprayed at a cost of 

 fifty cents an acre for the use of the plane. The plane was used on the 

 marsh lands as well as waterways. The results are striking, and large- 

 scale applications of hormone-like herbicides on forest areas, cereal crops, 

 and swamp land can be predicted with certainty. 



Let us try to look beyond the present horizons for plant hormones 

 and predict some of the things to come. We shall have hormone-Uke 

 selective weed killers for every conceivable use — for corn fields, wheat 

 fields, orchards, gardens, forests, waterways, swamp lands, hedge rows, 

 and yards. Any hormone which has specificity in its effects is likely to 

 find special uses. Perhaps the forest can be sprayed to kill all but pines 

 or other desired species. With a little stretching of the imagination we 

 can picture a lawn without crab grass, a bayou in Louisiana without 

 water hyacinth and aUigator weeds, pastures without thistles, onion fields 

 not weeded by hand, and helicopters available for spraying at twenty- 

 five cents an acre. 



Bud-inducing chemicals are seriously needed. They would facilitate 

 propagation of plant parts where buds have not appeared or where they 

 have been lost. Day liUes, Gloriosa lilies, and dahlias are often lost because 

 the storage organ does not have a natural bud. Internodes which do not 

 normally produce adventitious buds could be used for propagation 

 purposes. A shoot-inducing substance should cause new shoots to arise 

 where desired on the plant to make possible propagation of budless 

 parts or improve the shape and appearance of intact plants. There is no 

 end to the conceivable uses of bud- or shoot-inducing substances. 



Flower-inducing substances which are thought to exist in nature may 

 be isolated, identified, and used as a common tool. If this becomes a 

 reality it should be possible to force long-day types to flower during 

 short days or short-day types to flower during the long days. In short, 



