Profs. Percv Frankland and Marshall Ward. 



13 14 15 16 17 18 19 iO i\ U. 3 24 5 ib & 8 29 SO 31 5 53 34 35 3fc 57 38 39 40 

 T'ue ordinates are minutes, the abscissae temperatures. 



Summary. 



We see from various experiments e.g., those of November 17 and 

 18 that growth can and does take place as low as 8'5 C., but so 

 slowly that it is extremely inconvenient to get a curve sufficiently- 

 long for my purposes. When we remember that it takes from about 

 360 to 400 minutes, or even longer, for a filament to double its length 

 at these temperatures, it is obvious that one cannot trace many of 

 them ; for even supposing 360 minutes to be the average, it would 

 mean twelve hours' continued attention to get two doubling periods, 

 to say nothing of the six hours or more necessary for germination, so 

 that variations impossible to watch may take place during the long 

 intervals between some of the observations. 



Consequently I have but few records of these slow periods at low 

 temperatures near this. 



It is interesting to note, however, that 85 C. is certainly not the 

 minimum, though it probably approaches it ; this is important in 

 connection with the river habitat of the organism. 



Some of the experiments show that the growth is still very slow at 

 temperatures near 10 12 C., but it- is impossible to say more thin 

 that the doubling period is here about 300 to 400 minutes or so. The 

 observations begin to be more definite near 14 C., and we may put 

 the normal doubling period at not far from 200 minutes. 



