MICHIGAN ACADEMY OF SCIENCE. 25 



pots were sown with oats alone and a similar number sown with oats accom- 

 panied by a vigorous looking underground shoot of Canada thistle. Besides 

 oats the following were used in a similar arrangement: barley, buckwheat, 

 wheat and flax. In connection with these .sets another pair was arranged. 

 Young elm trees were planted one each to a 6-inch pot and oats grown 

 alongside. 



A numl^er of accurate measurements and oljservations Avere made from 

 time to time and records made. A summary of these present results partly 

 seen in the accompanying photographs, which represent not the extreme 

 but the average results as well as could be estimated. In photograph 1 

 to the left are the pots of oats, 1 and 2 having thistles planted with the oats, 

 while 3 and 4 have oats alone. In the same photograph to the right, are 

 four 6-inch pots sown to. buckwheat, 1 and 2 having thistles planted with 

 the buckwheat while 3 and 4 are clean. With the oats the thistles seem to 

 do no harm and if anything tend to increase the crop. The buckwheat 

 shows the result exactly opposite. Now, these results are not intended to be 

 final by any means. They are only calculated to represent one set of experi- 

 ments carefully carried out. 



In photograph 2 the oats when accompanied by the elm tree (about 10 

 inches high) indicate a poorer crop than oats alone. 



Whether these results would appear under other .-ondjtions and in other 

 kinds of soil is something we cannot predict. Experimental answers are 

 the only answer to the question. It is not as yet an easy matter to account 

 for this; yet it may be fair to suppose it arises out of one of two causes, (1) 

 Injurious excreta which might injure directly the roots of the neighboring 

 i:)lant or might tie up soluble nutritive matter of the soil. (2) This is the 

 exact counterpart of the ])receding, where we might imagine excreta to stimu- 

 late favorably the roots of a neighboring plant, or to release nutritive material 

 otherwise unavailable. 



Incidentally it might l)e worth while to give the results of one or two obser- 

 vations of the seedlings earlier in the season. 



In 22 days after planting, it seemed quite clear that the thistles stimulated 

 the oats, barley and wheat distinctly. This was more particularly notice- 

 able in the smaller pots. The results appeared much more pronounced 

 than at the time when the photographs were taken (58 days after planting). 



Not far from where these pots were placed in the garden, there grew a 

 young poplar tree about two and one-half inches in diameter. Corn was 

 planted in the garden about the tree. The crop of corn within a radius of 

 six or eight feet of the poplar tree was so distinctly poor as compared with 

 the corn in other parts of the garden, that I concluded I had a rival experi- 

 ment but not of my own ]3lanning. That such a result Avas not a matter of 

 shade was proved by the fact that in another portion of the garden similarly 

 situated with reference to the corn was a black locust tree nearly the same 

 size. The crop of corn in the neighborhood of the locust tree was about the 

 same as the average of the garden crop. Another ol^servation showed 

 that it was not a matter of shade. In a field of corn in this neighborhood 

 there grew an oak tree which was cut down and removed just about the time 

 the corn was planted. Now the crop of corn was so poor around the stump 

 of this tree that every passer by could not fail to notice it. The matter of 

 shade was of course entirely eliminated. It must have been a soil question 

 ])urely. Such field observations might be called supplementary and in a 

 sense they are more important and more conclusive than those conducted 

 * in pots. 



East Lansing, April 15, 1909. 



