1902.] SiTOEiL SUIE-NCES OF PHILADELPHIA. 4»3 



plaut on which it is growing, but L, confined to certain portions of 

 the stems or leaves. The mycelium of most of. the n««oy^J«; 

 eunial-that is, the mycelium which has produced a crop of spore» 

 (fi.~ 29, 30) one year, will the next year, under ordinary circum- 

 stances, produce another crop in or near the same place. The 

 explanation of the difference in the character of the cUtferent 

 abnormal growths produced by the various speces 'of Gymno- 

 sporangia i^ to be sought in the amount and extent of the n.ycehum 

 tie rapiditv of its growth and hs dumtion. We have m a rap. Uy 

 crown., annual species, viz., G. maa-opm, a large, rather spongy 

 e^xcresclnce, which shrivels in drying. The excrescence is more 

 deu.^ in the perennial species of slower growth, viz., G. <jlohomm. 

 The mycelium of G. bUeptatum, according to Farlow, is compara- 

 tivelv 'limited in amount, and does not increase rapidly, and m 

 consequence the formation of the annual wood layers is not pre- 

 vented, nor the nutrition of the branches above much inter eied 

 with The myceUnm, as described by Farlow, is found prmcii>ally in 

 the region of the cambium, and acts rather as a stimulant than as 

 a destructive agent. There is in G. EllUU . more 1---' - 

 rapidly "rowing mycelium, which extends along the .mallei 

 blthes'and is^abumlant enough to interfc wiUi the nutrition of 

 the infected branches. The consequence is that the branches above 

 become short and stubby, and at length densely '»-^'='»'^< • ^ "'^ 

 branch below the fungus remains normal in character, so that in- 

 steacl of a nodose swelling we have a tuft of short branches borne 

 on the end of a normal branch." ,. ■ .i 



With this brief resume of the chai-acter of the mycelium m the 

 different species of G,j«mo-n^ra,ujhm living in the wood of con- 

 iferous trees, it is important to make a more de.adec study of Uie 

 character of the mycelium and its relation to the cells of the ho^t 

 n Gy,n„o>pora>vi,«n H,.pM.un., Very little of a definite charac- 

 ter can be ascertained by a study of the transverse section of the 

 diseased wood of the white cedar. Here and there the cut «ids 

 of the hyph. are seen, and ocsionally the kunck e-l.ke porU.m 

 of one thai is bent is seen in the cross-section (flg^. 18, W). Hk 

 hyph*, which aie instrumental in stimulating the proiluction ot 

 additional wood and bast, live in the cells of the wood cambium. 



-» See ante. 



