Light in Greenhouse Culture 65 



is not due to temperature. It is due solely to the 

 effect of various light rays. Lilac blossoms, for in- 

 stance, if enclosed in a dark chamber will become 

 discolored, irrespective of surrounding temperatures. 



Coleus plants grown in a white hothouse will 

 produce leaves with the normal amount of red color 

 and pigm.entation. In a red hothouse, the red pig- 

 ment of the Coleus decreases, the leaves are more 

 spread, and their form is changed. Coleus grown 

 under green-colored glass produces leaves of small 

 sizes, the pigments almost disappear, and give place 

 to a yellow coloration. The same is true also when 

 Coleus is grown under blue glass. In this case, 

 however, the red pigments disappear almost com- 

 pletely (fig. 9, a-d.). In substantiation of the 

 fact that light is capable of transforming plants, 

 Flammarion refers us to the following experiment: 

 Coleus plants may gradually be transformed when 

 grown under a slightly diffused light through a gar- 

 den frame, in diffused light, and in still weaker 

 light. The plants grown in the open are of course 

 normal. The most curious transformation occurs 

 in the diffused light. Here the leaves enlarge con- 

 siderably and the red pigments diminish in the cen- 

 ter. Under a weak light the Coleus leaves become 

 stunted, and the color changes from poppy red with 

 a dark edge to yellow with a light green edge (fig. 

 9, e-h.). Purple leaves of Alternanthera amena will 

 become green under red glass. In the open, gera- 

 nium leaves possess a reddish brown tone. This color 

 changes under red, green or blue rays (fig. 10, a-h.). 



