214 
On Straio- Blight. 
through the intercellular spaces, and penetrates the cellular 
tissues themselves in every direction (Figs. B, C), more or 
less breaking them up from its rapid increase, and ulti- 
mately passing into the hollow interior (Fig. B, /;), which 
it fills with masses of delicate, matted, cotton-like threads 
(Fig. A). As soon as the straw is attacked, the vital action of 
the plant is affected ; and as the fungus develops, it completely 
stops the circulation of the sap, by cutting off the connection 
between the roots and the foliage. If the disease attacks the 
wheat before the period of flowering, the plants are hopelessly 
destroyed. The disease, however, appears generally to show itself 
at a later stage of the life of the plant, when the ear is beginning 
to fill ; and then, if there be sufficient food and vigour in the 
healthy upper part of the wheat to enable it to send out fresh 
roots from the lowest healthy joint, and to re-connect the living 
part with the earth, the growth of the spike which has been 
interrupted will be renewed, and the ears, though never filling 
completely, will nevertheless yield a partial crop. Even at the 
best, the ears of diseased stems, from the direction of the food of 
the plant to the formation of new roots, and froYn the diminished 
supply of food even when the new roots are in active operation, 
remain small, and when dry, are shrivelled and wrinkled, from 
being only imperfectly filled. Indeed the farmer generally de- 
tects the occurrence of this pest among his crops by observing 
the sickly aspect of the spike. 
No observer has yet noticed the fructification of this fungus, 
and as the classification of this group of plants is entirely based 
on the organs of reproduction, it is impossible to determine 
without them the genus, or even the group, to which this myce- 
lium belongs. 
Duthartre has detected on plants affected by straw-blight 
several species of other parastic fungi, such as Cladosporium 
lierbarum. Link, Septoria Tritici, Desmazieres, and Erysiphe 
f/raniiins, De Candolle. It is, however, certain that the mycelium 
of straw-blight does not belong to any of these known species. 
It was observed in 1851 that both barley and rye, as well as 
wheat, were attacked by this straw-blight in the valley'of Ville- 
preux, in France. 
The disease has been noticed in Belgium, as well as in France 
and England. It has been very irregular in its appearance, 
having been absent from a locality for many years, and then 
appearing and producing serious injury to the crops. ' It is 
estimated that in some districts in France it reduced the yield of 
grain in 1851-1852 to one half ; but the injury is seldom so severe 
as this, being gonorally from one-twrntietli to one fiftieth. ' 
The nature of the soil has nothing to do with the disease, as 
