186 Puget Sound Marine Sta. Pub. Vol. 1, No. 17 



Rindfleisch and De Bary. Vines (29) says that light exercises a retard- 

 ing influence on the growth of the sporangiferous hyphae of Phycomyces. 

 Jost refers to Stameroff's data showing increased rate of growth of the 

 conidiophores of Mucor when darkened. Granz (13) records similar re- 

 sults. Lakon (17) describes the favoring influence of darkness on the 

 vegetative growth of Coprinus. 



The destructive effect of sunlight on bacteria has been demonstrated 

 many times. Ewart (7) says that both chromogenetic and non-chromo- 

 genetic bacteria including those which contain chlorophyll and grow nor- 

 mally when exposed to diffused daylight may be killed by the prolonged 

 exposure to direct sunlight, and that even the vitality of the spores may 

 be affected. 



The work on algae has been rather limited. Berthold (7) (Rev. 

 Bot. Centralb.) found that intense light causes increased rate of elonga- 

 tion at first, followed by retardation, then entire cessation of growth if 

 the illumination is continued. According to Pfeffer, Kny reports more 

 active growth of Coleochaete on the illuminated side ; Noll and others 

 found that the "chlorophyllous assimilating branches of Caulerpa and 

 many other algae develop mainly on the side exposed to light." In Olt- 

 mann's (19) experiments, however, the effect of light was to inhibit ger- 

 mination and vegetative growth, and to accelerate spore formation. Ewart 

 (6) states that the green zj^gotes of Hydrod.ictyon may remain living if 

 dried in darkness, but if exposed to light, become decolorized and die. 

 That there is difference of opinion as to whether sunlight is beneficial or 

 injurious to algae is shown by the following sentence taken from West 

 and West (30) : "In the paper by Mr. Ewart we find the following state- 

 ment: 'It is well known that prolonged exposure to direct sunlight is 

 fatal to ... many algae.' From our own experience we should 

 at once say that nothing could be more beneficial to Freshwater Algae 

 than prolonged exposure to direct sunlight, provided they remain under 

 natural conditions." An example is given of accelerated growth in lower 

 green and blue-green algae exposed to direct sunlight all day. In Ewart's 

 next paper (7) he explains that direct sunlight on a pond may not pene- 

 trate the water because of reflection and refraction at the surface. He 

 experimented on the resistance of Chara to strong light and found that 

 the end cells are bleached after 6-8 hours' exposure to continuous sunlight, 

 death following bleaching when the whole cell is exposed. According 

 to him Spirogyra is bleached by one day's exposure to direct sunlight and 

 temporarily loses its power of assimilation. Schimper (25) says that 

 intense light is fatal to protoplasm independent of the action of heat; and 

 that algae are specially sensitive, some being killed by the increased 



