2o8 Journal of Agricultural Research voi. xiii, No. 3 



The pycnidia which form on leaves or stems of K. latifolia (PI. 15, A, B) 

 are very small compared to those on steamed white com meal, and on 

 steamed-potato cylinders. Those occurring on the leaves vary all the 

 way from 75 to 500 ^jl in diameter. The majority, however, are small, 

 usually about 250 iu in diameter. On steamed corn meal the pycnidia 

 are from 0.5 to 5 mm. in diameter, the average being 2 mm. On the 

 leaf of K. latifolia the color of the fruiting bodies is dark brov/n, almost 

 identical with the color of the dead leaf tissue surrounding them. On 

 culture media the color varies as stated elsewhere, being usually gray 

 white or dark greenish olive to dark ivy-green. On the host the p3-cnidia 

 are not deeply embedded, but are subepidermal and usually somewhat 

 flattened and roundish (PI. 15, A), There is no beak. No stroma is 

 formed on leaves or stems. The outer wall of the pycnidium is rough 

 and on sectioning is seen to be somewhat carbonaceous, of parenchyma- 

 tous texture, and irregularly thickened, the thickest portion being 

 toward the top (PI. 15, D). The majority have but a single chamber. 



The pycnidia on culture media are much larger than on the host. 

 They are also much more irregular in form, but usually are roundish and 

 somewhat flattened (Pi. 16). The carbonaceous wall is very much 

 more pronounced than on the host. The outer surface is smooth and 

 velvety in appearance. A cross-section of a pycnidium produced on 

 steamed com meal is shown in Plate 16, D, E. It is seen to be made 

 up of very small pseudoparenchymatic cells, the majority of these cells 

 being not over 10 ju in diameter. Usually the pycnidia on culture media 

 are many-chambered. Frequently the chambering is limited to the 

 outer portions of the pycnidium, and the cells are then coarser and show 

 a more or less radial arrangement. Upon approaching the portion 

 which is producing the spores, the parenchymatous structure is gradually 

 lost, and only interlacing hyph^ appear, which are here very promi- 

 nently nucleated (PI. 16, E). The sporophores are borne upon a more 

 or less carbonaceous mat of hyphae. 



STERiiyE PYCNIDIA. — In the cultural tests conducted, it has been found 

 that a large number of the bodies formed (usually upon a stroma) are 

 sterile. The structure of these bodies is shown in Plate 17, A, B. It is 

 identical with the internal central structure of a pycnidium which is 

 producing spores only at its margins. In all the numerous sections 

 made of these sterile bodies, small areas have been found at different 

 points along the periphery, showing interlacing hyphae prominently 

 nucleated (Pi. 17, B), and vv^hich suggested to the writer that these 

 bodies vv^ere really potential pycnidia, since areas similar to this are the 

 spore-producing portions of the pycnidia. Not much time has been 

 expended in determining this point, but the following experiment was 

 repeated several times, and in each test spores were produced in 75 to 

 100 per cent of the bodies used in the experiments. From 6 to 25 (in 

 one experiment 60) of these sterile structures were selected from the 



