420 



GROWTH OF PLANTS 



12 3 4 5 6 



y T ^'T'^rm 'y» ^'''V' ' aii 'j^ iW»t»f « | >qywCT^^ ■ i ^ v^tr^^^ 



Figure 168. Seed (Scott's lawn mixture) treatment involving three of the most effec- 

 tive synthetic "plant hormones," a commercial preparation (Rootone), and talc. The 

 chemicals were mixed with talcum powder and the seed dusted with the preparations. 

 The concentrations were at the rate of 1, 2, and 3 mg of the substance per gram of talcum 

 powder. Top rows: 1-3, three different concentrations of indoleacetic acid; 4, talc control; 

 5-7, three different concentrations of naphthaleneacetic acid. Lower rows: 8, non-treated 

 control; 9-11, three concentrations of indolebutyric acid; 12, talc control; 13, "Rootone," 

 commercial preparation; 14, non-treated control. 



the published results of other scientific laboratories, are that vitamin Bi 

 has been hadly exploited, and that it has no value as recommended for horti- 

 cultural practice." 



Importance of the Mother-Tuber in the Growth of the 



Potato Plant 



Denny i^- ^® undertook to determine the importance of the mother-tuber 

 to the development of the potato, also how long it must be retained on the 

 vine to insure maximum growth of vine. He developed a clever technique 

 for removing the mother-tuber from the plant at any stage of develop- 

 ment without seriously disturbing the soil or interfering with the root sys- 

 tem that had been established up to the time of removal. This method is 

 shown in Fig. 169. 



The mother-tuber was removed at four different stages of development 



