76 DUDLEY MEMORIAL VOLUME 



■ From these three averages of the lejigths of mustard seedlings — 4.32 

 cm., 4.02 cm. and 4.28 cm. — it is clear that, so far as the growth of the 

 hypocotyledonary stem is concerned, it makes no material difference whether 

 the plant is illuminated mainly from one side or on all sides successively. So 

 far as I could see, the seedlings all presented a normal appearance, both in 

 stems and cotyledons, as to size, color and form. 



This experiment having failed to throw ' any light on the question, I 

 sowed wheat similarly on III, 15, 1912, and put five pots on the quarter- 

 minute turn-tables, five pots on the half-minute turn-tables and five on the 

 shelf beside them. Four weeks after sowing I measured them, from the sur- 

 face of the soil to the tip of the unopened leaf, with the following results : 



Average length of 10 seedlings in Pot I on M-minute turn-table. 13.2 cm. 

 7 " " II 11.6 



7 " " III 15.2 



3 " " IV 16.2 



7 " "V 17.3 



" " 34 " 14.7 " 



Average length of 9 seedlings in Pot I on J^-minute turn-table. 17.1 cm. 



10 " " II 16.3 

 12 " " III 9.6 



11 " " IV 12.9 

 4 " "V 14.0 



46 " 13.98 " 



Average length of 6 seedlings in Pot I on the shelf. 9 . 68 cm. 



18.63 

 13.45 

 12.7 

 15.3 



41 " 13.95 " 



This experiment also, so far as the growth of the stem is concerned, 

 throws no light on our question, for there is no material difference in these 

 averages, of 14.7 cm., 13.98 cm. and 13.95 cm. There was, however, a 

 difference in the length of the leaves, which unfortunately I did not realize 

 in time to measure. But the leaves of the seedlings on the turn-tables were 

 in many instances as long again as those of seedlings on the shelf. Here, 

 then, we do have a resemblance to the behavior of the fern-prothallus and the 

 liverworts. In both instances we have chlorophyll-containing photosyntheti- 



