Feb. ai, 1916 
Soilstain , or Scurf , 0 / Sweet Potato 
999 
(PI. LXXVII, a, t , «). They are erect, not branched, and when viewed 
hastily would be mistaken for setae of species of Colletotrichum or Vermi- 
cularia. Upon a close examination they are found to be made of closely 
septate dark-celled mycelium, the base of which rests on one or two 
smaller ones (Pl. LXXVII, a). Generally the measurements of the 
conidiophores vary with the medium used. The host, too, seems to have 
a determining influence. 
In material collected at random from the market or direct from storage 
the conidiophores appear to be smaller than those taken from artifi¬ 
cially infected sweet potatoes. In the latter case, the causative organism 
seems to possess more vigor, because of moisture under control methods. 
The average of nearly 500 measurements on various media and on the 
host shows that the conidiophores vary from 100 to 300/x in length. 
Great difficulty was experienced in studying the formation of conidia. 
It is difficult to observe spore formation on storage material. Harter (4) 
claims that there is but one conidium formed at one time at the tip 
of the conidiophore. As soon as this conidium breaks off, a new one is 
formed in its place. The studies of the writer on this point are at va¬ 
riance with those of Harter. The writer finds that the spores are borne in 
distinct chains. In pure culture the chains break up very readily when 
moistened and pressed down with a cover glass. The spore chains break 
immediately when moistened with alcohol, oil, or any other liquid (PI. 
LXXVI, fig. 2, k y d, b). The chains of spores do not appear to be held 
together with any kind of mucilage. However, it was found that when a 
dry cover glass is carefully placed on the surface of a colony growing in a 
Petri dish and the latter placed under the microscope, all the stages of spore 
formation could be studied with much ease. The spores are borne in chains 
(PI. LXXVI, fig. 2, a t i, and LXXVII, g, h). At first, the protoplasm of the 
tip of the conidiophore is seen to round up, then a minute bud pushes out 
(PI. LXXVII, c) and increases in size until a mature spore is developed, 
which is left standing at the tip of the conidiophore (PI. LXXVII, d). 
All the succeeding newly formed conidia are formed at the tip of the 
conidiophore, so that the oldest conidium stands at the farthest end 
of the chain (PI. LXXVII, e , /, i). Careful observations of these chains 
have shown them to be made up of from 10 to 28 conidia. A distinct 
characteristic of the latter is that they are always guttulate (PI. LXXVII, 
m)y irrespective of the medium used. In some cases the conidia in pure 
culture appear to be massed in “pockets” around the tip of the coni¬ 
diophore, as in species of Gloeosporium or Fusarium (Pl. LXXVI, fig. 2, 
c, e t g> h, /). However, a close examination will show that this is no 
definite characteristic of the fungus. 
It has been stated that the least disturbance will cause the chains of 
conidia to break up. In so doing they invariably cluster around the 
conidiophore, grouping themselves in various ways (Pl. LXXVI, fig. 2, 
