SCHREINER AND REED: EXCRETIONS BY ROOTS 297 
means that the roots behave nearly the same whether the tubes 
are surrounded by fresh or used agar, and that the toxic effect of 
the agar in which corn has grown is small, the used agar being, 
in fact, practically as good as if freshly prepared agar had been 
used. 
WHEAT SUCCEEDING COWPEAS. 
The same method of procedure was followed as in the previous 
experiments. 
(a) Wheat plants in tubes containing fresh agar and surrounded 
by agar in which cowpeas had grown. —The results of four experi- 
ments employing 82 roots are tabulated. 
i es 
Experiment No. gig tn of | — bhi Inhale | Per Cent. Response. 
Hains viele aati 
I 12 | 8 | 67 
2 38 21 | 55 
3 23 9 | 39 
4 9 | 6 67 
Average response for the four samples of agar, 57 per cent. 
(6) Wheat plants in tubes containing agar in which cowpeas had 
§rown and surrounded by fresh agar.— The four experiments 
corresponding to the above employed a total of 96 roots; the 
details are here given in tabular form. 
: Roots Capable of Roots Which Grew | Per Cent, Response. 
Experiment No, hasatiar | Out of Tubes. | REV Lorain sens Seo conc 
; ac | If | 55 
- 31 23 | 74 
: ao 17 } 65 
3 . i 38 
Average response for the four samples of agar, 63 per cent. 
The results of these two sets of experiments are closely simi~ 
lar to the preceding experiments, which employed agar in which 
corn had grown. That is to say, it makes little difference so far as 
this Tesponse is concerned, whether the used agar is outside or 
inside of the segmented tubes. The results in the experiments 
With cowpeas are in the proportion of 90:100. 
This jis interpreted to mean that the excreta of the cowpea 
foots are very slightly toxic to roots of wheat seedlings. 
