116 



other side; the branch passes through the trunk a Hctle to one 

 side of its center, bridging the space between the two trees. The 

 branch extended several feet beyond the pierced trunk but ulti- 

 mately died. Two photographs were taken just after the pruning 

 of the tree had been accomplished and in the one reproduced 

 on page 115 the ladder used in the operation is seen still resting 

 against the bole of the tree. The butt is four inches in diam- 

 eter and appears to be emerging from both the bole and its 

 branch. The probable explanation of this condition is that 

 when both trees were young, a branch of one crossed a branch 

 of the other, resting firmly in the axil or crotch formed by the 

 bole and its branch; the friction caused by the natural growth 

 of the parts involved, assisted by winds and storms, probably 

 wore away the barks until the cambium layers were reached, 

 when a union of these tissues took place resulting ultimately 

 in completely covering the intruding branch with wood and 

 bark of the other tree, bringing about the present appearance 

 which might be likened unto that of "Siamese Twins." This 

 process resulted in the gradual strangulation, cessation of 

 growth, and death of that part of the branch beyond the tree; 

 the other part or "bridge" continued its growth and its union 

 with the tree is so perfect that its bark is as normally contin- 

 uous with that of the pierced trunk as with that of the parent 

 tree. 



Department of Botany. 



Parke, Davis and Company, 

 Detroit, Mich. 



AN UNPUBLISHED LETTER BY GRONOVIUS 



By Helen A. Choate 



This letter from Gronovius to John Bartram, the original of 

 which was recently acquired and is now in the historical collection 

 of the botanical library of Smith College, seems never to have 

 been published. Both because of the light it throws on the 

 current botanical life of that time, and as showing something of 

 the relations then existing between scientific men of Europe and 



