THE FUNGI WHICH CAUSE PLANT DISEASE 145 



D. willkommii Hart.^^ causes a serious European larch disease 

 and affects also the pine and fir. 



The stromata appear as yellowish-white pustules on the bark 

 soon after its death. Here hyaline conidia are produced on the 

 open surface or in cavities. Apothecia 2-5 mm. broad appear 

 later. The ascospores can infect wounds: the conidia seem to be 

 functionless. The myce- 

 lium spreads through the 

 sieve tubes, intercellular 

 spaces, and xylem to the 

 pith. 



Apothecia short^stalked, 

 yellowish without, orange 

 within; asci 120 x 9 /i; 

 spores 18-25 x 5-6 /i; 

 paraphyses longer than 

 the ascus. 



D. resinaria Rehm ^* is 

 a wound parasite much 

 like the above in its ef- 

 fects. It occurs chiefly on 

 spruce and larch but sometimes also on pine, both in Europe 

 and America. 



Ascophores upon cankers on branches and trunk of the host, 

 very similar to those of the preceding species but with more evident 

 stipe and paler disk; spores very minute, subglobose, 3 x 2-2.5 /i; 

 conidia 2x1 fi. 



D. calyciformis (d Wild.) Rehm occurs on several conifers; 

 D- subtilissima (Sacc.) on flr and larch; D. abietis Sacc. on Picea. 



Fig. 102. — Lachnella. F, habit sketch ; G, ascus 

 and paraphyses. After Rehm. 



Lachnella Fries (p. 135) 



This is similar to the last genus but with the apothecia usually 

 sessile and the spores usually 2-celled at maturity, and in two 

 rows in the ascus. There are about forty species. 



L. pini Brun.*' injures pine twigs. The apothecia are brown 

 outside; the disc reddish-yellow with a white margin. 



Ascoma short-stipitate, 5 mm. in diameter, pale brown; disk light 



