27 



tivo plants, thoso with colored foliage, as well as ordinary plants. 

 The experiment might he prolonged as long as desirahle. and j)rob- 

 ably unlooked-for i-esnlts would occur as to the form or color of the 

 organs, particularly of the leaves. 



Permit me to recall on this sul)ject an experiment made in 18r);5 by 

 Professor von Martins. It will interest horticulturists, now that 

 plants with colored foliage become more and more fashionable. 

 Professor von ISIartins placed some plants of Amdidnflixs tricolor 

 for two months under glasses of various colors. Under the yellow 

 glass the varied tints of the leaves were all preserved. The red 

 glass rather impeded the development of the leaves and produced at 

 the base of the limb yellow instead of green; in the middle of the 

 upper surface, yellow instead of reddish brown, and below, a red 

 spot instead instead of purplish red. With the blue glasses, which 

 allowed some green and yellow to pass, that which was red or yellow 

 in the leaf had spread, so that there only remained a green border or 

 edge. Under the nearly pure violet glasses the foliage became almost 

 uniformly green. Thus, by means of colored glasses, provided they 

 are not 3'ellow. horticulturists may hope to obtain at least temporary 

 eflFects as to the coloring of variegated foliage. 



The action of electricity on foliage is so doubtful, so difficult to 

 experiment upon, that I dare hardly mention it ; but it can easily be 

 understood how a building constructed as proposed might facili- 

 tate experiments on this subject. Respecting the action of plants on 

 the surrounding air and the influence of a certain composition of the 

 atmosphere upon vegetation, there would be by these means a large 

 field open for experiments. Nothing would be easier than to create 

 in the experimental hothouse an atmosphere charged with noxious 

 gas and to ascertain the exact degree of its action by day and by 

 night. An atmosjjhere of carbonic-acid gas might also be created, 

 such as is supposed to have existed in the coal period. Then it would 

 be seen to what extent our present vegetation would take an excess 

 of carbon from the air, and if its general existence was inconven- 

 ienced by it. Then it might be ascertained what tribes of plants 

 could bear this condition and what other families could not have 

 existed, supposing that the air had formerly had a very strong pro- 

 portion of carbonic-acid gas. 



In hopes of realizing this idea of a complete botanic laboratory, the 

 author spent his vacation of 1893 in the botanic gardens and green- 

 houses of Harvard University. On his return to Washington Pro- 

 fessor Riley kindly offered him every convenience and space in the 

 insectary of the Department of Agriculture. His 800 experimental 

 plants of wheat and maize were, therefore, brought hither from Cam- 

 bridge, Mass. But unforeseen difficulties arose, and it is to be hoped 

 that the idea of an experimental laboratory for botanic study may 

 be carried out by abler hands. 



