646 Journal of Agricultural Research vci.xxiv,no.8 
attained. Cross walls then appep,r, the first formed segments being 
further reduced in size by later successive divisions. Although at the 
time a segment has just undergone division, the appearance under the 
microscope is that of a thin line extending across the spore, the proto¬ 
plasts thus delimited soon round up along the zones where cross walls 
are in contact with the external wall. The latter in the hyaline-spored 
forms seems to undergo no readily perceptible increase in thickness; in 
the dark-spored forms the subsequent apparent increase in thickness is 
quite considerable. In the process of maturation the individual seg¬ 
ments appear to deposit a membrane of their own, the matured spore 
thus consisting of the original outer spore wall, inclosing a row of 
more or less independent segments, like peas in a pod. In some species, 
as for example, Helminthosporium leersii, where the outer wall is 
relatively delicate, these segments may be removed readily from their 
enveloping membrane by tapping or gently pressing on the cover glass. 
The process often results in no injury at all, each segment being capable 
of germinating independently and promptly. 
The mode of germination characteristic of a species usually bears a 
more or less apparent relation, both to the shape of the spore and the 
structure of its wall. In most of the forms with cylindncal hyaline 
spores, where the peripheral wall is everywhere uniformly thin, germ 
tubes are produced more or less indiscriminately from all segments, 
basal, apical, and intermediate. In the species with tapering spores, as 
H, dictyoidesy for example, one germ tube usually arises from the distal 
cell, and one or two from the larger basal cell, the intermediate segments 
rarely participating directly in the process. The germ tubes are not 
polar in position, but arise from undifferentiated regions usually laterally 
or obliquely at some distance from the hilum or the extreme apex. The 
fully matured spores of H, sativum and closely related species have two 
perceptibly thin places in the peripheral wall, these being located at the 
tip and at the base of the spore, in the latter case occupying a narrow 
zone adjacent to and surrounding the hilum. These areas may be 
clearly seen, for example, in H. monoceras. Here normal germination 
takes place by the production of one germ tube from the thin-walled 
region at the tip, or from that near the hilum, or more often from both; 
never from the intermediate segments, unless, as has been mentioned, the 
latter have been partly exposed or completely liberated from the en¬ 
veloping wall by manipulation or mechanical injury. In some other 
forms like those later discussed under the names //. halodesy H, rostratumy 
and H, oryzaCy germination of entirely mature spores takes place as in 
H. sativum and H, monoceras, but not infrequently newly proliferated, 
subhyaline spores, the walls of which have not become tiiickened, can 
be seen to produce, in addition to the two polar germ tubes, one or more 
tubes from the middle cells as well. 
A modification of the septa, visible in the spores of some species, and 
undoubtedly present in others, may be not wi^out significance in germi¬ 
nation. If the cross walls of large, subhyaline-spored forms, like Hel¬ 
minthosporium teres or H. giganteum, are closely examined a small circu¬ 
lar spot having perhaps one-fifth or one-fourth the diameter of the spore 
may usually be distinguished. It is difficult to determine whether this 
represents an open communication between the segments or merely two 
opposed pits in the adjacent segment walls. The appearance of these 
walls in plasmolyzed dead spores would suggest that the latter alternative 
is the more probable one, a suggestion that is supported by the fact that 
