MICHIGAN ACADEMY OF SCIENCE. 31 



that all three seedlings (pea, lupine, corn) tolerated a solution strength 

 of V32- None grew in ^/le, the next grade stronger, 



A saturated solution of lime employed in a similar manner gave the follow- 

 ing result. All three seedlings grew in a solution strength of one-eighth, 

 but none grew at one-fourth, showing that when the supernatant Bordeaux 

 is compared with saturated lime water, it is found that the Bordeaux is four 

 times as toxic. 



Bordeaux mixture whole, i. e., the precipitate and supernatant liquor 

 together, presented another interesting problem. When the Bordeaux is 

 fresh, i. e., when used within a week or ten days after its preparation, the 

 seedlings withstand a strength of about Vi28, both corn and pea, but not 

 the lupine, growing in this. When the Bordeaux mixture is allowed to stand 

 a month or so, similar seedlings withstand then a strength of about ^ /204s- 

 This is about 16 times as dilute as that in which the test was made with 

 freshly prepared Bordeaux. 



Another difference which developed was this: If Bordeaux be prepared, 

 well shaken and divided into two portions, one set aside as it is and the other 

 diluted to about ^ / 20^, arid then set aside, in four or five weeks after this, 

 tests made with both show that seedlings withstand (of that not diluted 

 till used) a strength about four times as great as that diluted when prepared. 

 These phenomena were shown particularly with the lupine. These radicles 

 ahvays turned yellow showing by this some reaction with the liciuid which 

 was not apparent with either of the other two seedlings. In fact the lupine 

 became yellowish in solutions as dilute as 1 /8i92- 



As a matter of fact Bordeaux mixture should not be any more toxic than 

 the supernatant liciuid, because the copper, which is the toxic element, is 

 in the form of an insoluble precipitate, and consecjuently as such could not 

 react upon the radicle of the seedling. The experiments above mentioned 

 show that the mixture is at least four times as toxic as the liquid alone. 

 This excessive toxicity is clearly due to an interaction between the radicle 

 and the precipitate, indicating that roots of plants can react chemically 

 upon insoluble compounds in the solution. As has already been pointed out, 

 this was especially noticeable with the lupine. 



A number of vials of the various grades of the diluted Bordeaux was .set 

 aside for several months, some of them for more than a year, and then it was 

 seen that the copper underwent during this time some decomposition, because 

 a dark brown precipitate appeared in connection with the blue, in from one 

 to six months; and this appears more particularly in certain grades of dilution 

 commencing at about one-fourth. The whole Bordeaux, full strength, 

 underwent the least apparent decomposition as indicated by the absence 

 of any formation of free copper, or of copper oxide. 



One very peculiar result developed especially with the corn seedlings. 

 Corn repeatedly grew in a strength of supernatant liquid of one-fourth 

 while it would not grow in one-eighth. This phenomenon was observed 

 by the writer in experiments reported in the tenth report of the Michigan 

 Academy of Science, 1907, p. 60, concerning fungus spores. Some of the 

 experiments there described indicate that spores would germinate at a certain 

 dilution, and fail to germinate in the next one or two grades more dilute. 

 No explanation was offered at the time, but now it seems reasonably clear 

 that the comparatively rapid decomposition which goes on in more dilute 

 solutions is accountable for this rather striking phenomenon. For ex- 

 ample, corn grew in a dilution of one-fourth and failed to grow in one-eighth. 

 This can be explained by assuming that the more rapid decomi^osition in the 



