654 STATE BOARD OF AGRICULTURE. 



surface of the leaf, or as in many cases only slightly, with the peridium 

 remaining intact, the only factor entering into tlie forming a ''l)roa(l -os- 

 tiole" is this pressure of spores. Spores begin to form after the peridium 

 has developed exactly as they are produced in culture (see above). As 

 soon as one spore is formed another arises from the undifferentiated 

 hymenial layer. In such a manner, spores are produced in great abund- 

 ance until they completely fill this pycnidium. This mass of spores 

 becoming larger and exerting a gradually increasing force upon the thin 

 3-5 celled wall, suddenly hreaks through this pycnidial wall at the point 

 of least resistance. This point of course is usually the part of the pyc- 

 nidium nearest the upper or lower epidermis of the leaf. At no time 

 has a definite pre-formed ostiole been observed in culture or in the leaf. 

 In culture, the mass of spores finding the weak point in the pycnidium 

 in the submerged part of the fruiting body, forces itself into the agar 

 (Plate 7, Fig. 2) breaking off the lower half of the wall, the remains of 

 which were easily determined. It will be recalled by those who have 

 seen various Sphaeropsidales in culture that the presence of an ostiole 

 can often be clearly distinguished before spore exudation. The entire 

 pycnidial formation in this fungus is strikingly different from that in 

 the regular ostiole-forming pycnidia. There is no doubt but that in this 

 matter of presence or absence of ostiole we have a phenomenon which 

 could readily be made of taxonomic significance. (Von Hohnell 1911). 



The Natne of the Causal Organism: 



Recently Diedicke (1912) in his critical revision of the Genus Sep- 

 toria, limited this genus to forms whose fruiting layer is enclosed in a 

 pseudopycnidial case, which is equipped with a more or less broad open- 

 ing. This work was strongly confirmed by the previously published 

 work of Klebahn (1908) and Potebnia (1910). At this point the work 

 of Potebnia may be cited rather fully. 



In a chapter on Septoria, Phleospora, and Ehabdospora he writes, 

 ''These three genera were in general placed with the Sphaeropsidales, 

 while in Saccardo's Sylloge (III, 577; XI, 398; XXI, 975) the position 

 of the genus Phleospora is not determined and is placed with both the 

 Sphaeropsidales and the Melanconiales. Those species belonging here 

 which were studies by me show that the three genera are closely related 

 and properly do not constitute typical Sphaeropsidales forms, because 

 the fruiting bodies are not built as typical pycnidia. The commonly 

 tender wall of the fruiting body consists of a network of hyphae, which 

 lines the cavity in the leaf tissue made by the destroying activity of the 

 fungus. Such fruiting bodies are named "Pseudopycnidia." The de- 

 velopment on artificial substrata in the majority of species of the three 

 genera studied is in agreement. At first the conidia-forming mycelium 

 is produced, then there arise the "Klumpen" or "Ballen," in which Kle- 

 bahn has shown for Phleospora ulmi, pycnidia (Septoria or Phleospora), 

 and micropycnidia (Phyllosticta) are formed." 



So firmly convinced is Diedicke (1912) of the potency of this dis- 

 tinguishing characteristic and of. its taxonomic importance, that he 

 would exclude all forms lacking this pseudopycnidium from what he 

 considers true Septorias. This he has already done with at least two 

 species. Diedicke would put the forms possessing Phoma-like pycnidia 



