202 SUMMARY OF CURRENT RESEARCHES RELATING TO 



By means of the medullary rays, the fungus is able to penetrate deep 

 into the wood ; it grows luxuriantly in these rays, and also in the vessels ; 

 in the woody tissue it is intracellular, but in the softer tissues of the leaf 

 it is confined to the intercellular spaces. It is impossible to diagnose 

 the fungus from the appearance of the mycelium ; the nature of the 

 host-plant can, however, be deduced, as, for instance, when the host 

 contains oil, as in the UmbelHferffi, where there are oil-globules present 

 in the mycelium. He notes specially the differences between the mycelium 

 of LeptosphcBria Rusci on Ruscus aculeatus and on R. Hypoglossum. 

 In the former it is of narrow lumen, in the latter broad and full of oil- 

 globules. The size and form of the ripe perithecia are also conditioned 

 by the position in which they grow and by the contents of the surround- 

 ing host-tissue. 



Franz Duysen * has made a similar study of some forms of Disco- 

 mycetes in the several groups Pezizineaj, Phacidiines and Hysterinea?. 

 The Discomycetes possess a branched, septate mycelium which forms at 

 times a considerable growth of loose hyphte and of plectenchyma. 

 There is no sharp distinction between vegetative and fruit-forming my- 

 celium. Duysen has examined and describes in full detail the liabit and 

 growth of fifteen species, and sums up his results at the end of the paper. 

 These coincide largely with those arrived at by the previous writer in his 

 study of the Pyrenomycetes. The mycelium encounters the same series 

 of tissues and grows under the same conditions as already described. As 

 before, the medullary rays and the vessels are attacked most readily. 

 Somewhat more attention has been given to the penetration of the wood- 

 cells. The liyphffi enter and leave these cells through the pits, and very 

 often there is a swelling of the hypha as it approaches the pit, and again 

 after it passes. The passage through the pit is narrower than the 

 hypha, so there is a massing of plasma contents both before and after 

 the constriction. The same substratum offers similar difficulties or ad- 

 vantages to all fungi growing on it, so the different fungi attack it in 

 the same manner, and the direction followed by the mycehum of any 

 fungus is due entirely to the physical conditions of the tissues. 



Sclerotinia Coryli.t — H. C. Schellenberg records a case of this 

 fungus occuiTing in the axis of the male flowers of the hazel. The 

 diseased catkins were in the winter condition, and the pollen-sacs were 

 undeveloped, so infection must have taken place in the autumn about 

 the time when the catkins were first formed. Those attacked dry up ; 

 they remain on the branches till spring, then fall to the ground, and 

 apothecia are not formed until the following spring. The first sclerotia 

 are formed in the cortical parenchyma, stray hyph^e pass out to the 

 epidermis, while others push inwards through the medullary rays to the 

 pith, where another sclerotium is built up. The sclerotia do not possess 

 an outer sheath, that layer being supplied by the destroyed tissues of 

 the host-plant. The author did not get any Mo?iiUa growth, but he is 

 convinced that the Monilia that occurs in the ovules belongs to the 

 same fungus as the sclerotium of the male catkins. The biology of the 



• Hedwigia, xlvi. (1900) pp. 25-56 (7 figs.). 



t Ber. Deutsch Bot. GeselL, xxiv. (1906) pp. 505-11 (1 pi.). 



