24 BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. 
and put forth a very blunt apex. All are composed of a corky, 
parenchymatous, very dense, soft yellow material. The mature 
ones attain a diameter of 3 to 4 millimeters and a height of 1 to 2 
millimeters, and on the somewhat reddish, and finally rusty red to 
yellow top, they are marked by black points, the ostioles.” The 
Tulasnes observed that before the stromata reached their full size 
the pycnidial cavities were formed within them, sometimes “ widely 
open,” sometimes “narrow labyrinthine,” and that through one or 
many openings in the top of the pycnidia, the long, twisted, orange 
tendrils, composed of mucus, and innumerable thin linear spores 
were expelled. “Perithecia are developed chiefly in stromata des- 
titute of spermogonia, or more often with onlya few * * * they 
arise very abundantly and irregularly, some barely buried in the 
yellow corklike substance, others lower down and seemingly located 
in the bark of the host itself.” 
Although the Tulasnes included all their material under a single 
species, they noted that the pycnidial stromata of the American 
specimens (really Endothia gyrosa) differed considerably from the 
European (Z. fluens). In describing the former, they say (83, p. 
88) “The American fungus is said to grow in the bark of Fagus 
and Juglans * * * asa whole it abounds with numerous, very 
small spermatia. Wherefore if it is very thinly sectioned, the pieces, 
examined with a compound microscope, show cavities just as if you 
had before your eyes the smallest Gautieria or Balsamia.” The 
Tulasnes do not try to distinguish definitely between stroma and 
mycelium, but merely state that the stromata develop within the 
mycelium. 
Ruhland (67), who was the next writer to discuss the morphology 
of a species of Endothia, defines the various portions of the fungus 
body in detail. According to his definition (p. 16) a “stroma (in 
distinction from mycelium) is the sum total of that part of the 
vegetative portion of the fungus body, which, without serving ex- 
clusively for absorption, takes part in the formation of the fruit 
body.” He sets aside Fuisting’s (36, p. 185) division of the fungus 
body into an epistroma and a hypostroma, as essentially nothing but 
the distinction of “ conidial layers” and “ perithecial stroma.” 
Ruhland divides the fungus body into an ectostroma and an ento- 
stroma. The ectostroma grows “on the upper surface of the paren- 
chyma of the bark, between it and the periderm, and is composed of 
a generally wide-lumened plectenchyma which does not possess the 
power of absorption.” This portion has the following functions: 
“The formation of the conidia, the opening and breaking off of the 
periderm, and the stimulation of the development of the entostroma.” 
The entostroma, on the other hand, according to Ruhland, “ lives in 
the parenchyma of the bark, and while young is in a high degree 
