MICHIGAN ACADEMY OF SCIENCE. 47 



produced by white light we can not be snre that it is prodnced by white 

 light at all. It is very probably not. Moreover, the coloring matter in 

 the red and the brown algae are said to serve the function of modifying 

 the light rays so that the portion of the spectrum which reaches the 

 protoplasm may be tempered to the protoplasm upon which it acts. 

 The brown coloring matter is suited to a considerable depth of water. 

 The red coloring matter of the red algae, makes it possible for these 

 plants to live at a greater depth than the brown algae live. At great 

 depths of water the prevailing light is bluish, and the red coloring mat- 

 ter in the algae have probably to do with modifying this blue light to 

 suit the needs of these plants. It has been observed that the maximum 

 assimilation of carbon dioxide occurs in a different part of the spec- 

 trum in sea-weeds from that of ordinary green plants. This apparent 

 difference is probably again due to the fact that different conditions 

 are required to produce a given luminous effect upon the protoplasm, 

 although it is quite probable that a certain portion of the spectral light 

 produces a similar effect upon all plants. The difficulty is that we 

 do not as yet know just what portion of the white light reaches the 

 protoplasm, even when we apply certain portions of the spectrum to 

 the plant. So that the whole matter resolves itself into this : Although 

 white light, or direct sunlight, is the kind of light which is received by 

 the external parts of the plant, yet the light which is ultimately applied 

 to the protoplasm, is, in all probability, only some portion of white 

 light, i. e., some color. And, it is only reasonable to suppose that, in 

 the course of development of the race of plants, if a certain color pro- 

 voke a stimulus useful to plant functions, such would be retained and 

 developed in the course of evolution. This could be brought about by 

 developing tissue, or cell contents, or both, of certain refractive values. 



The economic aspect of these deductions, is not without some signifi- 

 cance. Light has, without doubt, an important formative influence 

 upon plant structures. If a portion of a branch of a potato plant be 

 kept in darkness, a tuber, or tubers, will be formed. If in the light, 

 leaves and branches are formed. It has also been shown that certain 

 portions of the spectrum have a formative influence. This has been ob- 

 served in some of the Mucors. Sporangia will form under certain colors, 

 and not under others. Then again, it has been noted that, abnormal 

 growths occur under the influence of certain colors. This affords a sug- 

 gestion fruitful of results, because man might improve to his advantage 

 such abnormal growths as would prove useful. 



As has already been shown, certain colors stimulate in one direction, 

 and other colors, where other functions are under consideration, in 

 other directions. This gives rise to great possibilities. Eed stimulates 

 growth more than yellow; while yellow is more active in photosynthesis, 

 i. e., starch production. Blue and violet have greater formative influ- 

 ences. Intelligent regulation of these stimuli might give man a chance 

 to augment his food and fibre supply. Glass houses of colored glass 

 could be made, therefore, important pieces of apparatus to develop this 

 idea. The larger the houses, the more nearly natural the conditions 

 would be ; and houses, not bell-jars, are very desirable, so that plants 

 could be cultivated through the whole course of their lives under nearly 

 natural conditions, — a thing much to be desired. 



Agricultural College. 



