156 BOTANICAL GAZETTE. [ July, 
the band in my first experiments. Material collected from 
other places also failed to produce the results expected. 
This pointed to some special local condition as the cause of 
the peculiar action of the band. Investigation showed the 
following facts: f 
The pond was formed by the waste water of a blast fur- 
nace. Its water was always warm. Its sandy bottom was 
warmer than the water. In the coldest weather it never 
froze. (This last fact is given upon the authority of employés 
of the furnace.) Thermometric tests showed that when the ; 
temperature of the air was from 16° to 20° F. that of the 
water of the pond was from 68° to 76° F., while that of the 
ottem was from four to seven degrees higher still. The 
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filaments grown inthe tub. After numerous trials, I sue 
ceeded, by the use of a series of water baths, in securing 4 
temperature of from 70° to 90° F which was reasonably aaa 
stant. I then cultivated some of my ‘* unresponsive” Spiro- 
gyra with this added condition. It grew with astonishing 
rapidity. Examining the tilaments thus crown, I found the 
exact conditions noted in those collected from the blast fur 
nace pond, and a repetition : d the 
' of the ex s produce é 
same results. : e€ experiments | 
