Il6 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. 



-A, 



FIG. 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. , 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 I st, then bring gradually into a forcing 



