434 



Plant Physiology 



developed in the dark ; (2) upon structures formed previous to 

 placing the plants in the dark. 



Secure the same variety of any plant grown in half-shade and 



in an exposed situation ; 

 compare the two with re- 

 spect to structural modifi- 

 cations, water-content, and 

 extent of root system. 



Light and blossoms. 

 Place over carnations, just 

 coming into blossom, aer- 

 ated bell glasses, one of the 

 bell glasses being covered 

 with manila paper or un- 

 bleached cotton. Follow 

 the effect of severe shading 

 upon the opening of flower- 

 buds of other plants which 

 were equally advanced at 

 the outset. 



Killing effect of light. 

 FIG. 123. Potato sprouting in a dark, Prepare in a Petri dish a 

 moist atmosphere. dilution culture of any 



species of bacteria convenient, using the minimum quantity of 

 the clearest agar obtainable. When the agar is solidified, expose 

 the cultures about one hour to direct sunlight, protecting, how- 

 ever, a portion of the dish by means of darkened cardboard. 

 Replace the cover of the dish, incubate the cultures for several 

 days, and note the effect of the exposure to light. This experi- 

 ment cannot be carried out where laboratories are not equipped 

 for the cultivation of micro-organisms. 



REFERENCES 



BAILEY, L. H. Some Preliminary Studies of the Influence of the 

 Electric Arc Lamp upon Greenhouse Plants. Cornell Agl. 



