260 RELATION OF PLANT PROTOPLASM TO ENVIRONMENT. 



sulphur spring in California, and in washings from marine algse of Hawaii. 

 Many similar records to these would suggest a plasticity and adaptive capacity 

 at the present day that seem only possible of explanation as due to long continued 

 exposure to altering environment. That so many freshwater and cool species 

 have developed is probably due to geographic isolation and subsequent adaptation 

 to a uniform and stable set of surroundings, in certain originally primitive types. 

 The writer graphically proved nearly two years ago that certain of them 

 can resist great extremes of temperature, of drying and of insolation. For on a 

 macadamized road leading from Morgarten to Schwyz, he watched, for two weeks, 

 numerous examples of a nostocaceous species that grew from between the broken 

 road metal. These shrank to small semi-leathery flecks when hot summer suns 

 made the stones warmer than the hand could comfortably bear ; they rapidly 

 became swollen up when rain fell for an hour or two, while in winter they were 

 exposed on the inclined road to temperatures greatly below that of the freezing 

 point. A temperature range of 70°-75° C. seemed a concomitant of their annual 



life cycle. 



Under the eighth heading, it would be impossible in the present paper to 



discuss at length the question of color variations as shown by the thermophilic 

 algse, and the possible relation of these to the important question of chlorophyll 

 evolution. Suffice it if we here say, that from the physiological knowledge we 

 now have of yellow, yellow-brown, yellow-red, purple-green, and blue-green 

 schizophyceous pigments, it seems likely that we have here to deal with possibly 

 one, perhaps two series of color compounds, that may all be capable of utilizing 

 the sun's rays in the elaboration of synthetic plant foods. 



Weed's graphic description therefore of the color gradations seen in many 

 hot springs deserves quotation. He notes that as the water from a spring "flows 

 along its channel it is rapidly chilled by contact with the air and by evaporation, 

 and is soon cool enough to permit the growth of the more rudimentary forms 

 which live at the highest temperature. These appear first in skeins of delicate 

 white filaments which gradually change to a pale flesh-pink farther down stream. 

 As the water becomes cooler this pink becomes deeper, and a bright orange, and 

 closely adherent fuzzy growth, rarely filamentous, appears at the border of the 

 stream, and finally replaces the first-mentioned forms. This merges into yellow- 

 ish-green which shades into a rich emerald farther down, this being the common 

 color of freshwater algse." 



The ninth line of inquiry has been already sufficiently touched on in the 



foregoing paragraphs, and need not detain us. 



The second great group of the Protophyta is the Schizomycetes or Bacteria. 

 Even more diverse views have been propounded, as to their cytology, than o 

 the blue-green or schizophyceous series. We would regard them as being com- 

 posed of a mucilage-cellulose or cellulose membrane, which in many of the m 

 motile forms seems to be permeated by nitrogenous compounds. The pro 

 plasm, as in the previous group, is rich, granular, and abundant; sap vacuoles 



