84 



The Canadian Field-Naturalist. 



[Vol. XXXV. 



ifers", Proceedings of the Society of Am- 

 erican Foresters, Vol. XI, No. 4, (October 

 1916) p. 394, Prof. Harold S. Newins, As- 

 sociate Professor of Forestry, Oregon Agri- 

 cultural College, calls these stumps "Grow- 

 ing Stumps", and refers to the fact that 

 they may be found growing vigorously and 

 yet isolated as far as 20 feet from any 

 growing tree (I have found t)iem 50 feet). 

 He says: "When found so isolated, the 

 common belief has been that they subsist 

 by drawing on a reserve supply of food 

 materials which have been stored within 

 their bodies and roots." He finally says 

 that such "Growing Stumps" are the re- 

 sult of conjunctive symbiosis, which is 

 made possible by their root-graft wit/i a 

 living tree. The two investigators on the 

 Pacific Coast have therefore no hesitation 

 in ascribing the cause of the overgrowth 

 to natural graftage of roots with growing 

 trees of the same species. 



When, some years ago, I learned that the 

 root-graft theory of the cause of the vital- 

 ity and overgrowtyh of the stumps was 

 doubted, I went to considerable expense in 

 having doubtful-looking cases tested by ex- 

 cavation of the roots and in every instance 

 the root-graft was established. It seemed 

 that a very slight graft was sufficient, and 

 that the host tree need not be very large 

 to accomplish the overgrowth of a stump 

 of a tree of greater size. I found it diffi- 

 cult to discover a stump very remote from 

 other trees. The scattered large Douglas 

 Fir of the original parklands of the vicin- 

 ity w^ere mostly still standing and the 

 young growtih was generally in dense for- 

 mation. There was one instance in which 

 a group of nine capped-over Douglas Fir 

 stumps were distant over fifty feet from 

 a large tree and there was absolutely no 

 indication of roots of the stumps and tree 

 being anywhere near each other; never- 

 theless, excavation proved that actual root- 

 graft existed. The roots of the big tree 

 stretched at a depth of two feet below the 

 surface past the group of smaller trees, 

 the tap roots of some of w/iich had become 

 grafted to the underlying roots of the big 

 tree. These stiunps, so grafted, were in 

 turn root-grafted to others more remote 

 and all were overgrown alike. This, I 

 think, shows that apparently remote stumps 



may really be root-grafted to growing trees 

 by a series of concealed, unsuspected root- 

 grafts. The more especiallj- may this be 

 so as frequently the major parts of the 

 stumps are decayed and portions of roots 

 only remain vital. This phase of the ques- 

 tion, in my opinion, explains how remote 

 and apparently isolated stumps can show^ 

 bulky overgrowt^i. There is probably a 

 chain of root-grafts connecting the stump 

 with living trees. I have never been able 

 to learn of an overgrown stump proved, 

 by actual and complete excavation of all 

 its roots and rootlets, to have no direct or 

 indirect root-graft with foliage-possessing 

 trees. The great spread of the lateral roots 

 of conifers may not always be realized, 

 and this, combined with indirect root- 

 grafts, may enable overgrown stumps to 

 have a source of elaborated food in a dis- 

 tant forest. In fact, it is hard to say 

 whether the translocation of elaborated sap 

 would ever stop as long as there were liv- 

 ing stumps and direct and indirect root- 

 graft wit/1 sufficient canopy of foliage. 

 The question could be easily settled exper- 

 imentally, as well as the point whether one 

 species is more potent in this respect than 

 another. The grafting together of the 

 roots of separate trees should be of easy 

 accomplishment artificially in a single 

 season, and then, if the stems of those trees 

 intended to be used for tests were cut the 

 following year, an immediate overgrowth 

 should commence in species prone to s^ow 

 the characteristic. The stumps in some 

 species of conifers are said to respond 

 more quickly than others. I have observed 

 the phenomenon in Douglas Fir (Pseudot- 

 suga taxifolia, (Poir.) Britt.) and in Grand 

 Fir {Ahies grandis, Lindley) only, the 

 Douglas Fir being far more potent in over- 

 igrowth than the Grand, Fir. In botji 

 species, when the overgrowth is cut off, a 

 renewed ^lealing takes place. I have never, 

 however, seen a healing and overgrowth 

 by means of secondary or indirect root- 

 graft in the Grand Fir. Stumps showing 

 healing and overgrowth abound in all dis- 

 tricts in the vicinity of Victoria. In the 

 Douglas Fir the heartwood of the stump 

 is usually charged with resin and a com- 

 plete capping takes place. In the Grand 

 Fir the heartwood nearly always decays 

 and a rim only of live wood ensues, T^e 



