May 36, J993 
Graminicolous Species of Helminthosporium 
647 
t^ch segment suffers death independently of the others. There can be 
little doubt, however, that this modification provides means of com¬ 
munication between adjacent living segments. Such a communication 
would manifestly be of importance especially in those species in which 
germ tubes are produced only from the two end cells. There are, it 
may be mentioned, peculiarities in the germination of some species 
that can not be definitely ascribed to the structure of the septa or of the 
peripheral wall, or indeed to any demonstrable structural feature; as, 
for example, the production of liiree germ tubes from the basal cell of 
H. dematioideum, or the proliferation of clusters of tubes from the end 
cells or middle cells in H. giganteum. 
It is interesting to note that if leaves bearing actively sporulating 
fructifications of forms possessing thin-walled, hyaline spores, like 
Helminthosporium teres or H. hromi, are examined under the microscope 
by reflected light, it will be seen that the mature spores lying about in 
some abundance are badly distorted and their walls utterly collapsed. 
When these spores are mounted in water, most of them instantly become 
turgid, and at a suitable temperature begin to germinate within 30 
minutes, showing that the collapsed condition is by no means an indica¬ 
tion of death. Dead spores or dead segments of partly living spores, 
also present in a preparation, recover their former size and shape very 
largely, although not wholly, but are readily recognized by their abnor¬ 
mally swollen membranes and coarsely granular contents made familiar 
by the drawings and descriptions of many authors, who unfortunately 
regarded them as normal. Although some authors report germination of 
spores exhibiting such swollen walls presumably in all segments, either 
as a result of age or the application of reagents, the writer has never 
observed an instance of viability in such material. 
Germination is usually accompanied by conspicuous protoplasmic 
changes beginning in the segments concerned, and finally involving all 
the segments of one spore. The contents lose their uniform hyaline 
structure, becoming minutely granular or uniformly vacuolate, or more 
usually both granular and vacuolate. The germ tubes and mycelium 
in general vary somewhat with the different species. All the species 
seem to thrive on the culture media commonly employed in laboratories, 
which fact, together with the large size of the spores, makes the members 
of the genus among the fungi most easily isolated and cultivated. Not all 
of the species, however, can be made to sporulate in pure culture, those 
possessing hyaline spores— Helminthosporium hromiy H, tritici-repentis, 
etc.—^being especially refractory in this respect. The majority of 
forms with dark spores, on the other hand, sporulate quite readily and 
even abundantly, although the spores thus produced may depart some¬ 
what in shape and size from those produced under ordinary field condi¬ 
tions. This is particularly true of H. sativum^ where the spores, instead 
of being long and slender-allantoid, become shorter, thicker, and nearly 
straight. When media containing a large amount of nutrient is em¬ 
ployed, an abundant development of mycelium usually takes place and 
sporophores are produced in great numbers. Growth, however, soon 
comes to a standstill, leaving the sporophores short, and bearing only a 
few spores, the latter frequently being abnormally short. In such cases 
more satisfactory results can be obtained by the use of media containing 
little nutrient, as corn-meal-decoction agar or tap-water agar. If such 
cultures are protected from evaporation, the relatively small number of 
sporophores will continue to grow for several months, producing scores of 
