880 SUMMARY OF CURRENT RESEARCHES RELATING TO 



New Parasitic Fungi.* — Under the name Corijneiim Beyerinckii 

 C A. J. Oudemans describes a fungus parasitic on tlie branches of 

 AmygdaleJB, and wliicli he regards as frequently the cause of the 

 gummy exudation bo often found on them. It is found only in 

 the neighbourhood of the wounds from which the gum exudes, in the 

 form of dark spots, visible to the naked eye. They consist of a light 

 brown parenchymatous stroma, from which proceed a great quantity 

 of shortly stalked usually 4-celled conidia, distinguished by the great 

 facility with which they germinate when placed in water, and without 

 paraphyses. 



Discella TJlmi appears as minute swellings or internodes near the 

 apex of elm-branches, causing the leaves to turn brown and fall. 

 These swellings ultimately open, but are not perithecia, containing 

 only conidia borne singly at the apex of sterigmata ; they are oval or 

 obovoid, 14-16 /x long and 8-9 /x broad, and filled with a very fine- 

 grained protoplasm. 



Chestnut-disease.j — G. Gibelli has further investigated this 

 disease, so destructive to the chestnut-trees in Italy. The extremities 

 of the roots of the diseased trees he finds always infested with a 

 dense mycelium, resembling a pseudo-parenchymatous cap ; and the 

 rootlets are often enveloped by branched rhizomorphs. The smaller 

 roots are swollen into coral- or pear-like knots. The fructification is 

 of two kinds, conidia, belonging to Torula exitiosa de Seynes, and 

 perithecia, belonging to Sphceropsis castanece Sacc. var. radicicola ; 

 and the author believes these to be stages in the cycle of develop- 

 ment of the same species. The roots of sound specimens, not only 

 of the chestnut, but also of other CupuliferaB, were found to be infested 

 by the same mycelium, but without any fructification ; and Gibelli 

 thinks that as long as the tree is in other ways healthy, it is able to 

 resist the injurious influence of the parasite. 



The solid granulations found in the wood of the diseased trees 

 are not composed, as has previously been believed, of true tannin, 

 but of a crystalline acid nearly related to it. It occurs in the 

 form of sphfErocrystals of all sizes, up to that of a pin's head. In 

 polarized light they show a black cross. The sphterocrystals of 

 adjoining cells are in contact with one another by their bases. 



Cystopus.;}: — A. Zalewski has made a detailed examination of the 

 structure of a number of species of this genus of parasitic fungi. 

 The mode of abstriction of the conidia and that of the formation of 

 the zoospores have already been sufficiently described. 



The oospore is inclosed in a double coat, composed of endospore 

 and exospore, and in cultivated specimens he was able to trace the 

 development of the exospore with great exactness. The endospore 

 consists entirely of pure cellulose, and is not, as Cornu has stated, 

 composed of three distinct layers. The exos])ore, on the other hand, 

 is usually clearly differentiated into three layers. The innermost 



* Hedwigia, xxii. (1883) pp. 113-7. 



t Ann. (li Agricolt., 1882, and Mem. Acoad. Sei. Bologna, iv. (5 pis.). See 

 Bot. Ccntralbl., xv. (1883) pp. 116-7. Cf. thia Journal, i. (1881) pp. 282, 777. 

 J Bot. Ccntralbl., xv. (1883) pp. 215-21. Of. this Journal, ante, p. 084. 



