272 ASCOMYCETES. 



intercellular spaces, but it may also penetrate the wood as far 

 as the pith. The fungus only spreads during autumn and 

 winter, never during summer, the vegetative period of the 

 larch. The attacked tissues of the bark turn brown and shrivel 

 up, causing the depressed canker-spots. Healthy parts continue 

 their growth normally, and are frequently cut off from diseased 

 areas by formation of layers of secondary cork; this isolation 

 is, however, rarely effective, since fresh invasions of mycelium 

 from the wood into the bast take place annually, and thereby 

 the canker-spots keep enlarging for an indefinite time. 



The fungus develops reproductive organs only in damp marshy 

 situations. On this account spore- formation is less frequent on 

 mountainous slopes than in moist valleys and ravines. The 

 larch, on its first introduction into the low-lying parts of G-ermany, 

 Denmark, and England, was much cultivated as a pure forest in 

 close damp localities, and with great success ; but now this parasite 

 has followed its host from the mountains and causes ever 

 increasing damage. 



As preventive measures may be recommended : larches in 

 low-lying districts should be grown in open, airy situations, and 

 never massed together nor placed in the neighbourhood of diseased 

 larches. 



Lachnella. 



The reproductive organs are similar to Dasyscypha, but the 

 apothecia are firmer and generally have no stalk ; the spores as 

 a rule become two-celled at maturity. 



Lachnella pini Brunch.^ occurs in Norway on twigs of Pinus 

 sylvustris, as a parasite which quickly kills young plants and twigs. 

 It is rare on old plants. The apothecia resemble those of D. 

 Willkommii, but are larger, externally brown, and covered with 

 brown hairs and scales. The disc is reddish-yellow with a whitish 

 margin. The asci measure about 100^ by 9/u, and contain 

 colourless unicellular spores about 20/u long. 



Rhizina.^ 



This genus contains the single species Rhizina undulata 



'Brunohorst, Nogle norske skovsygdomme, Bergens Mus., 1892. 



-Rhizina has a position somewhere between the Pezizeae and the Helvelleae. 

 Saccardo places the genus under Pezizeae, while Sohroeter makes for it the 

 special group of Bhizmacei, included under his HelveUinei. 



