252 
W. P>. Mercer, 
a practicable one. From the small number I have been able to examine, 
however, their development appears to be similar to that described for the 
symphyogen. 
Perhaps the chief interest attaching to the pycnidia lies in the 
development of the primordium. The majority of the pycnidia whose 
evolution has heretofore been studied, form their primordia in one of 
the two ways. Thus it arises by the weaving together of hyphae in 
Diplodia mamillana 1 ) and in the Graphiola 2 ) studied by Alfr. Fischer. 
Meristogen growth, however, appears to be commoner — e. g. Pycms 
scier otivora 3 ), Curcurbitaria elongata 4 ), Cur cur bit aria Platanh), Lepto- 
sphaeria Doliolum 1 ), Fumago vagans 5 ). The extreme case of the for¬ 
mation of the pycnidium by division of the spore, finds a parallel in the 
direct development of pycnidia from ascospores of Curcurbitaria Platani *), 
when brought on to gelatine. 
Zopf 5 ) has shown that pycnidia of the same fungus may arise by 
either of these methods. The resemblance of the pycnidia on Calla fungus, 
in form and development, to the “Gewebefrüchte“ of Fumago vagans is 
striking. In both cases the general construction of the fruit is simple, there 
are no sterigmata, and there is no differentiation among the wall cells; 
the two differ only in that the pore is formed in Fumago by gélatinisation 
of the apical wall cells, whereas this does not occur with the GTz/Z^-fungus. 
They both stand in marked contrast to the more highly evolved types 
such as Septoria apii 6 ), Phoma apiicola 6 ), Curcurbitaria Laburni 7 8 ), 
Septoria atrip lieh s ) etc. in which the spores are borne on sterigmata, 
and the wall shows two types of cells, an outer, darker, layer and lighter 
isodiametrical cells towards the inside. 
Though the earlier stages in the evolution of the pycnidium of the 
Calla-hmgus present some similarity to that of Thelebolus stercoreus 9 ), 
there is no primary “fertile cell“ as in that fungus. Indeed Thelebolus 
would seem to be an isolated case of such a method of formation. 
4. The pycnidial spores. 
The spores are colourless, oval, or egg shaped, 6—7 g long, and 
4 g broad. Oil is characteristically present as two or three drops towards 
each end (Fig. 2, io ). Occasionally they are flattened, spherical, or ir¬ 
regular in shape (Fig. 2, //). Elongated spores with little or no oil are 
sometimes met with (Fig. 2, na)\ they do not, however germinate. 
1 ) Bauke, Beiträge zur Kenntnis der Pycnidien (Nova Acta 38. 
Nr. 5, p. 443). 
2) Fischer, Alfr., Beiträge zur Kenntnis der Gattung Graphiola (Bot. 
Ztg. 1883). 
3) v. Tafel, E., Beiträge zur Entwicklung der Pyrenomyceten (Bot. 
Ztg. 1886). 
4) Eidam, Über Pycnidien (Bot. Ztg. 1887). 
5) Zopf, Die Con id ienf rächte von Fumago (Nova Acta 40, Nr. 7). 
6 ) Klebahn, Krankheiten des Selleries (Ztschr. f. Pflanzenkrankh. 1910, 
20, H. 1). 
7) Tulasne, Select. Fung. Carpologia II, p. 215. 
8 ) Frank, Handbuch der Pflanzenkrankh., 2 . Aufl., 2. 
9 ) Brefeld, Untersuchungen aus dem Gesamtgebiete der Mycologie 
1891, H. 9, p. 114. 
