36 BOTANICAL GAZETTE [july 



escaping from the antheridia and swimming rapidly around the 

 eggs, then scattering as, presumably, one of them succeeds in 

 entering. The first cross -wall can be seen very plainly 24 hours 

 after the cultures are started. The mucilage accompanying the 

 eggs causes them to adhere so firmly to the bottom of the dish that 

 it is not necessary to use solid media to keep the sporelings from 

 being displaced when the cultures are moved to the microscope 

 stage for examination. 



The original plan for determining w r hich wave lengths are the 

 effective ones in the orienting action of white light upon the germi- 

 nating spores was to use the Wratten filter screens with the 

 electric arc. With this purpose in view, the set of seven screens W 

 borrowed from the physics department were analyzed as to wave- 

 length transmission, and the distances from the arc were found at 

 which the dark boxes with these screens as windows should be 

 placed to make the light intensity equal in all. After repeated 

 failures to get the spores to germinate on account of the high 

 temperatures produced by the naked arc at the distances at which 

 it was necessary to place the cultures, this source of light was 

 abandoned, as was also a 1000-watt Tungsten globe for the same 

 reason. Neither would the spores germinate when the boxes 

 w r ere placed in direct sunlight, as the heating effect was too strong, 

 especially behind the red filters. The first positive results were 

 obtained w r ith a mercury vapor lamp behind the blue, violet, and 

 ultra violet screens, the violet transmitting waves of 4000-4700 

 Angstrom units, the blue 4700-5200. The same effect was pro- 

 duced in these lights as is produced by white light, namely, the 

 first cleavage planes formed perpendicular to the direction of the 

 incident light, and the cell on the darker side of the spore became 

 the rhizoidal cell. This effect was not produced behind the green, 

 yellow, and red screens, behind which cultures were exposed at 

 the same time. This experiment was unsatisfactory, inasmuch as 

 it offered no way of proving that the other wave lengths were 

 less capable of producing the phenomenon than were those of the 

 blue end of the spectrum, because the blue light is so much more 

 intense in this lamp than are the red, yellow, and green. The prob- 

 lem was then dropped for several months, during which time no 



