THE PI.ANT WORIvD 57 



Spontaneous Fission of Olive Trees in 



Palestine. 



By Charles A. White. 



The olive is the most abundant tree of Palestine. It grows upon the 

 wild rocky hillsides and in the valleys by nature's planting, and less fre- 

 quently in cultivated grounds. It is never a large tree, but many of those 

 which one sees there are evidently very old — some of them perhaps 

 hundreds of years old. A few are well formed, but they are often gnarled 

 and misshapen. They are rarely, if ever, arranged systematically like 

 orchard trees, but I occasionally saw small, compact groups or clusters 

 of them from two to five in number. In some groups they stood so 

 closely together that their branches necessarily interlocked, but in others 

 they were several feet apart. Such groups, although most of the trees 

 are more or less distorted, are suggestive of artificial planting; but upon 

 examining a considerable number of them, as well as separate trees, I 

 became satisfied that each group of the kind referred to had originated by 

 spontaneous fission of an original tree. That is, I found olive trees in 

 various stages of vertical fission of the trunk upon lines corresponding with 

 its medullary rays. At first the cracks extended only a little deeper than 

 the thickness of the bark, but in others they had evidently become deeper 

 and deeper until the parts thus delimitated formed prominent vertical lobes 

 and finally separated into individual trees. Each original crack occurred 

 upon a slightly irregular line extending down to the roots from between the 

 bases of the principal branches, and the number of cracks was apparently 

 determined by the number of such dominant branches. Each one of those 

 branches thus became the crown of a separate tree, and each new tree 

 appropriated its portion of the original roots. Each separate trunk thus 

 produced by fission was as fully covered with bark as was the original 

 tree, and the new vertical coat was doubtless produced by the prompt 

 inflowing of new bark from the split edges of the old, just as the wounds 

 of trees are usually healed. As the fissures deepened, the new bark 

 evidently followed so closely that little or no exposure of interior woody 

 fiber occurred. 



What were the conditions of woody growth that caused the original 

 siurf ace cracks I do not know, but similar cracks in other trees are known 

 to occur. The crowding of new bark into the resulting fissures evidently 

 aided in separating the parts of the original tree from one another, but 

 that aiding force ceased with the severance of contact, and I am not able 

 to offer a satisfactory explanation of the further separation of the parts. 



