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HORTICULTURE 



March 24, 1906 



Symbiosis and its Relation to Horticulture 



In these days of horticultural advance we hear much 

 of the sterilization of soil and fighting the fungus 

 diseases in general, and but little of symbiosis, which is 

 the association of two organisms which live together 

 in intimate connection, both contributing to their 

 mutual welfare. Greater interest should be given this 

 subject, and evidence should be advanced toward the 

 possible advantage of using the principle in horticul- 

 tural methods. We unconsciously take advantage of 

 the method when we transplant evergreens with balls 

 of earth and find greater success attending this method 

 than where the roots are not accompanied with soil, or 

 become subject to even slight drying influences. There 

 are some curious seeming contradictions which, how- 

 ever, are doubtless to be explained away as we learn 

 more of the subject. 



In a nutshell the principle is that of the natural 

 replacement of the ordinary nutriment and moisture- 

 absorbing root cap of green leaved plants with the 

 mycelium of certain species of fungi who in return for 

 absorbing from the soil the principals of moisture and 

 nourishment and turning these ingredients over to the 

 green leaved plant, are supplied in exchange with cer- 

 tain principals of nourishment from the sap of the plant 

 itself. All of the blue berries, heaths, rhododendrons, 

 daphnes, empetrums, gecestas, a great number of coni- 

 fers, seemingly the entire oak family and numerous 

 willows and poplars, we know to be dependent for 

 nutrition on the assistance of various fungi, though 

 the full life history and identification of the species of 

 these fungi is yet to be determined. 



As regards the oaks and poplars, all the roots of these 

 genera are completely surrounded by the matted mycel- 

 ium growth of certain types of fungus and so closely 

 woven is this covering that there is no well defined line 

 of demarkation between this and the adjoining layers 

 of purely natural growth. Through this matted fun- 

 goid area are minute absorptive or feeding cells which 

 perfectly replace root hairs in their peculiar function. 

 Furthermore there is a distinct interchange of fluids 

 between this mycelium and the true hard wooded plants. 

 Under such circumstances it is not a difficult matter to 

 account for the comparative ease in transplanting oaks 

 and poplars because of their wide distribution whereby 

 it is difficult indeed to find areas that are not thoroughly 

 impregnated with spores of the necessary fungoid asso- 

 ciates, and provided every protection and moisture are 

 supplied during digging and transportation. The 

 beech, however, is a less cosmopolitan tree and with but 

 few specific forms, showing a greater dependence on the 

 exercise of care in keeping the roots moist during trans- 

 portation as well as so far as possible seeing to it that 

 there is a fair degree of soil attached to the roots during 

 the transplanting process. A failure to observe these 

 requirements always results in disappointment to the 

 planter except in occasional cases where by chance the 



tree is placed in a situation that lias already become 

 impregnated with the desired fungoid mycelium. 



Many, if not all, of the conifers are dependent largely 

 upon this means of obtaining nutriment, and in this 

 family the mycelium growth is frequently quite con- 

 spicuous. Evergreens provided with balls of earth in 

 which they have naturally grown suffer least loss in 

 transplanting. In this we get a world of suggestion as 

 to why certain plants can only be moved with difficulty 

 wherever the roots lose all of the attached soil or suffer 

 in the least from drying influences. We can also under- 

 stand from this why rhododendrons fail to succeed in 

 limestone soils when we know the inveterate antipathy 

 of limestone to fungi in general; we understand why 

 leaf mold is to a certain extent indispensable to the 

 cultivation of these plants that the necessary source of 

 fungoid growth may be present and as well the need of 

 good balls of earth in transplanting with the plants 

 themselves in order that the fungus in its living and 

 vigorous form may accompany the plant in its travels. 

 It seems that while the first roots of seedlings or cut- 

 tings are provided with the usual root cap, the vigorous 

 and healthy future growth of the plant is dependent 

 on the combination of two seemingly distinct forms of 

 vegetable life. 



While the above facts may not be generally known 

 yet they are not unparalleled in the vegetable kingdom, 

 for lichens as a class are absolutely dependent on the 

 association of two distinct vegetable divisions, that is, 

 the algse and the fungi, wherein each is in- the closest 

 association and dependence on the other for their 

 respective vegetative requirements, this partnership 

 extending even to the spores. On the other hand we 

 have ample evidence of late of the importance of certain 

 low forms of animal or bacteria life to the healthy 

 growth of such leguminous crops as alfalfa and clover, 

 though the efforts towards an artificial dissemination 

 of this through the so called bacteria cultures have not 

 been crowned as yet with unqualified success. 



The point that I am seeking then to bring out is that 

 of giving the importance of the principle of symbiosis 

 careful thought and the danger that may result from 

 destroying fungoid types which may be beneficial and 

 which if destroyed by soil sterilization may be to the 

 detriment of certain classes of plants which depend on 

 them for existence. Soil sterilization undoubtedly is of 

 the highest value in connection with the cultivation of 

 many green house crops, such as the carnations, the rose 

 family in general, as well as many vegetables, but we get 

 from this a hint that it may be an evil when practiced 

 with certain classes of plants whose absolute existence 

 is dependent on the assistance of fungi in their healthy 

 STOwth. 



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