390 SUMMARY OF CURRENT RESEARCHES RELATING TO 



is sufficient proof of the presence of the fungus, as the brown coloration 

 may be present in healthy plants. 



C. E. Klugkist * gives an account of parasitic fungi in north-west 

 Germany. Species of Plasmopara, Peronospora, several fungi imperfecti, 

 the Basidiomycetous Exobasidium on Rhododendrons, and various 

 Uredinea? are recorded by him. He adds an alphabetical list of the 

 hosts with the parasitic fungi that have attacked them. 



Mycorhiza.t — Gr. A. Duthie and D. M. Matthews made a superficial 

 and later a microscopic examination of twenty-six species of roots of 

 forest-trees to determine the presence and nature of any mycorhizal 

 fungi. Sixteen of those trees were found to have ectotrophic mycorhiza 

 on their rootlets, seven had the endotrophic form, and three trees, 

 ashes and willow, were apparently unaffected. The ectotrophic species 

 were the red, white and black oak, the tamarack, the Norway pine, the 

 chestnut, the American elm, the mockernut and bittern ut hickories, the 

 beech, the blue beech, the ironwood, the black cherry, the trembling 

 aspen, the poplar and the paper-bark birch. The endotrophic species 

 were the swamp and sugar maple, the basswood, the horse-chestnut, the 

 walnut, the butternut, and the sycamore. The trees grew in Michigan 

 in the vicinity of Ann Arbor. 



L. H. Pennington $ has also studied mycorhiza with a view to 

 identifying the fungi that are associated with the tree-roots. He traced 

 the connection between Russula emetica and red oak. A species of 

 Boletus with a yellow stem and yellow mycelium was also identified in 

 association with the roots of a tree ; the yellow strands were like 

 rhizomorphs and were traced down to the roots and to small yellow 

 sclerotia in the soil. Another fungus with yellow mycelium, Trkholoma 

 transmutans, was found to form the mycorhiza of the black oak ; the 

 mycelial threads were very abundant and were always found thickly 

 clustered about the roots and connected with a felt of ectotrophic 

 mycorhiza. 



L. Petri § reports a long series of observations on the mycorhiza of 

 olive trees. Several members of the Oleaceas have no fungus on their 

 rootlets, others have occasional mycorhiza. In the genus Olea there is 

 also great diversity, but in most of them the endotrophic form is more or 

 less constant. On the whole there is less development of the root 

 fungus in heavily manured or in damp situations, while in a dry 

 locality it is very abundant. In the interior of the roots the mycelium 

 is at first intercellular ; later the walls of the host-cells are pierced and 

 it becomes intracellular. Occasionally large vesicles are formed in the 

 inner cortex, and this phenomenon is specially marked in olive trees 

 that have suffered from a fungoid disease of the leaves caused by 

 Stictis Panizzei. Further he notes that mycorhiza is rare where there 

 is abundance of nutritive salts in the soil. In such soil the development 

 of the roots is rapid, especially at the stage of most active vegetation, 

 and in such conditions the higher plant becomes independent of the 

 endophyte. 



* Abh. Nat. Ver. Bremen, xix. 3 (1908) pp. 871-412. See also Bot. Centralbl., 

 ex. (1909) pp. 308-9. 



t Tenth Rep. Mich. Acad. Sci. (1908) p. 46. % Tom. cit., 47-49. 



§ Atti Reale Accad. Lincei, cccv. (1908) pp. 754-63 (3 figs.). 



