BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 449 
water are colored, not the characteristic red of this group, but shades of brown and 
green; for example, the Irish moss, Chondrus crispus, is frequently green under bright 
illumination in the summer at Woods Hole. Furthermore, Nadson (1900) has shown 
that certain species of the Cyanophyceze and Chlorophycer, which are green near the 
surface, take on reddish colors in deep water. 
These conclusions that the colors of algze depend upon the quality of the light are 
opposed to views held by Berthold (1882), Oltmanns (1892), and others who have con- 
sidered the Rhodophycez to be merely shade plants, the distribution of which was deter- 
mined by the quantity of light. They have made much of the fact that in dimly lighted 
caves and shaded situations red algz, which usually grow at some depth, are found very 
near the surface; but it should be borne in mind, as Bérgesen (1905, pp. 702, 703) points 
out, that while these alge receive a much weaker white light in these caves, they may 
have the benefit of much blue and green reflected light. 
Gaidukov (1902, 1906), in a series’ of interesting experiments, has shown that certain 
alge (species of Oscillatoria, Phormidium, and Porphyra) take on complementary colors 
when subjected to pure rays from a spectrum, becoming, for example, green under red 
and yellow light and red or purplish under green or blue light. This phenomenon, called 
complementary chromatic adaptation, is shown only by living plants and is believed to 
involve changes in the structure of the pigments. The reason why green alge can not 
live in deep water is clear, since the red rays upon which they depend are not there 
present. The red alge, on the contrary, may live at the surface as well as at depths 
below the penetration of red rays, but at the surface they meet the competition with 
green algee from which they are free in deep water. 
However, it can not be said that all of the phenomena are clearly explained by the 
hypothesis of chromatic adaptation held by Engelmann and Gaidukov. Thus, Rodriguez 
(1888) reports the following Chlorophycez off the Balearic Islands at much greater depths 
than would be expected for any of the green alge: Palmophyllum orbicularis Thuret, 
130 meters; Cladophora pellucida Kiitzing, 40 meters; Codium tomentosum Agardh, 48 
meters; C. tomentosum var. elongatum, 90 to 100 meters; Udotea Desfontainii Decaisne, 120 
meters; and somewhat similar records are known for certain of the Chlorophycee in the 
Gulf of Naples. 
7. TEMPERATURE AND SEASONAL CHANGES. 
The temperature of the water, the depth, and the character of the bottom are the 
chief factors in determining the distribution of the alge in the region covered by the 
survey. The influence of temperature must be of fundamental importance where the 
seasonal extremes are as great as those of the summer and winter at Woods Hole. ‘The 
conditions in the winter would admit a rich northern or boreal algal flora at Woods 
Hole were it possible for the species to reach this sheltered situation by traveling around 
Cape Cod and to survive the warm summer. As it is, a number of northern species do 
grow at Woods Hole in the favorable winter and spring seasons and some are able to 
vegetate through the summer. In striking contrast with the winter’s cold is the summer 
temperature, which is so high that it can support a flora with many points of resem- 
blance to the floras of warmer seas. The subject of temperature receives considerable 
attention in section 1, chapter 1, pages 38-52, where the detailed records of the Survey 
29 
16269°—Bull. 31, pt 1—13 
