Nov. 1897.] BOTANICAL SOCIETY OF EDINBURGH 69 



111 1885 Professor Frank published in the " Berichte 

 der Deutschen Botanischen Gesellschaft " a remarkable 

 paper, explaining in a quite unexpected manner the mean- 

 ing of the fungoid mantle which had been noticed in the 

 fine roots of the Scots fir, Pinus sylvestris, a few years 

 previously by Eees. 



He found that not only in the case of the Scots fir, 

 but also in the case of other conifers, and also most 

 markedly in the case of the Cupuliferae, such as beech and 

 the hazel, the finer and trophic roots were thickly en- 

 veloped in the mycelium of a fungus. The constant 

 occurrence of this fungoid envelope on the roots of all 

 the trees of these orders persuaded him that it could 

 not be an accident, and as he found that it existed on 

 the roots of even the youngest and healthiest specimens, 

 he felt satisfied that it could not be a parasite, or at least 

 a destructive parasite. He at once conceived the idea that 

 this was a case of symbiosis, and worked diligently at the 

 investigation of the roots of a great variety of plants from 

 that standpoint. Among these were roots that had been 

 sent to him from all quarters of the globe, and its presence 

 in them all showed that the fungus was universally dis- 

 tributed. This fungus, like others, lives upon organic 

 matter provided for it by other plants. It is found as a 

 fine thread-like mycelium ramifying through the mass of 

 organic matter left by the fallen leaves and debris of forest 

 trees, and is not met with where that organic matter is 

 wanting. AVhen a conifer or cupulifer is planted in such 

 soil, it is not long before its roots are fastened upon by 

 this fungus, and in time the growing points of the roots 

 become closely wrapped round with it. In ordinary 

 circumstances the growing rootlets of plants are beset 

 with fine hairs, through whose delicate walls the nutritive 

 mineral matter in an available soluble form passes from 

 the soil into the circulation of the plant. In the case 

 of the two orders referred to, when the fungus has 

 established itself, the trophic rootlets have no hairs. 

 Their place is taken by the fungus, from which proceed 

 numerous fine filaments, that at first sight might be 

 mistaken for hairs, but which, on microscopic examination, 

 are seen to be aggregated mycelium filaments. That these 



