PLATE 25 

 Relation of soil temperature to the development of onion seedlings. 



Upper row. — Seedlings of Red Globe variety 13 days old. Each cluster was the 

 entire crop from one experimental culture pot. All were grown in like virgin soil and 

 at the same air temperature (i5°to2o°C.) but with gradation in the soil temperature of 

 the respective pots as follows (left to right): 12° to 14°, 20°, 25°, 28°, 30°. Note that 

 there is a tendency for greater root development in relation to top growth at the lower 

 temperatures. This was especially marked at the lowest temperature, 12° to 14°. 

 For further details see Table V and the accompanying text. 



Lower row. — Seedlings of Yellow Bermuda variety grown imder same conditions as 

 those in upper row. 



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