134 MISS $. LONGMAN ON THE DRY-ROT OF POTATOES. 
type of spore obtained. In every case from each spore there pushed one, or 
frequently several germ-tubes. The germ-tubes soon branched and gave rise 
to the ordinary mycelium, which in its turn bore the usual typical spores. 
Massee finally states that after a long time blood-red flask-shaped bodies 
appear on dried up bits of skin that have been exposed to the open air. 
These fructifications he depicts as typical perithecia, each bearing a number 
of asci, and each ascus containing eight spores. No such fruits have been 
met with during this investigation, and that although the fungus has been 
kept under observation for several years. The last stages in the development 
of the Fusarium watched at Reading consist either in the pink pustules 
containing the typical Fusarium spores, or else in the blue mycelium, with 
its two peculiar types of spores. 
III. PARASITISM OF FUSARIUM. 
Tt has been thought that dry-rot is always preceded by wet-rot, but this 
is not the ease. +. Solani may infect tubers that have previously been 
attacked by wet-rot, but it is also quite capable of attacking healthy tubers. 
This was proved during the autumn and winter of 1907, when many 
healthy tubers were inoculated with the spores of К. Solani, with the result 
that the symptoms of the disease made their appearance in them. 
Smith and Swingle (04) have shown that the disease also invades the 
growing plant, and this my experiments confirm. They state that the fungus 
ordinarily enters the plant by the roots, and slowly spreads through all the 
underground parts of the plant. Аз the roots die the stems fall over, and 
the leaves and upper parts of the shoot wilt. Although the mycelium 
spreads throughout the root system, few or no hyphæ are found at the 
ground level, and as a rule, the brown staining only penetrates for a few 
centimetres above ground. 
During the summer of 1907 many of the potato plants grown for the 
purposes of these experiments in the ground neighbouring the Botanical 
Laboratory at University College, Reading, were attacked by Fusarium. 
The infected plants resembled in most particulars those described by Smith 
and Swingle, but differed from them in the following respects :— 
I. When the shoots began to wither the lowest, and not the uppermost, 
leaves were the first to become black and die ; the stems also died 
from below upwards. 
II. The brown staining frequently spread about half way up the stem, 
although it was never found in advance of the highest dead leaf. 
III. In some cases the stems died at the same time as the leaves, but in 
others they remained green and standing for some time after the 
leaves were dead. 
