n6 



•RELATIONS OF PLANTS TO LIGHT 



organs of the shoot. Make a plan showing the relative position 

 of the shoots and branches. 



176. Etiolation of Plants with, and without Aerial Stems. Se- 

 cure normal healthy specimens of rhizomes of Viola obliqua, 

 which sends only leaves and flowers above the surface of the soil. 



FlG. 53. Cross section of portion of etiolated stem of young Quercus. A, pro- 

 toxylem. B, median portion of thin wood-ring, in which the medullary rays are 

 larger than in the normal. C, cambiform tissue. D, bast, showing greater develop- 

 ment than in the normal. E, inner periderm. 



and also a similar number of Viola rostrata which forms a leafy 

 shoot. Allow these plants to remain in a cold house or out-of- 

 doors until December 1 st, then bring gradually into a forcing 



