THE PHOTOTROPIC SENSITIVITY OF PHYCOMYCES AS RELATED TO WAVE-LENGTH.

Under the circumstances of experimentation described, the sporangiophores of Phycomyces are found to be most sensitive to stimulation by light in the violet between 400 and 430 mmicro. Toward the red, sensitivity falls to nearly zero near 580 mmicro, while in the near ultra-violet around 370 mmicro, sensitivity is still high. The previous experiments of Blaauw had placed the point of greatest sensitivity some 80 mmicro nearer the red end of the spectrum. Because of the known presence in the sporangiophores of Phycomyces of "accessory" pigments, care must be taken in identifying such results with the absorption spectrum of the photosensitive substance.