116 



GROWTH OF PLANTS 



tree peony seeds when the seeds are planted in flats at different times of 

 the year and kept in cold frames, with board covers. Those planted during 

 the spring and summer of 1932 gave no seedlings until the spring of 1933. 

 During the summer of 1932 the roots grew and during the winter of 1932- 

 1933 the epicotyls after-ripened and seedhngs came up in the spring of 1933. 



Figure 46. The effect of low temperature on shoot development of Viburnum species. 

 A, V. acerifolium. B, V. dilatatum. C, V. -prunifoUum. 



The May planting gave the best results. This gave the roots adequate 

 time to grow mthout gromng so long that foods of the seeds were exhausted 

 before the epicotyl developed ready to manufacture foods. The earlier 

 plantings may have led to exhaustion of the foods of the seeds before the 

 epicotyls functioned, but the early decay of some of the seeds at the low 

 temperatures was also a factor. The July planting did not give sufficient 

 time for root development before the cold weather set in. The May plant- 



