NOTES ON THE ERYSIPHACEAE 9 
In many cases the perithecia of species of the Erysiphaceae appear 
to become free through the gradual dying away and disappearance 
of the mycelium. 
Some observations I have made on the spontaneous detach- 
ment and reversal of the perithecium in some species of Uncinula 
may be mentioned here. 
At p. 92 of my monograph I pointed out that the perithecia 
of Uncinula aceris are, from some cause, frequently turned over, 
and that the appendages which are thus pressed against the leaf, 
become mucilaginous and attach the (reversed) perithecium to the 
leaf. Some observations I have made since show that this phe- 
nomenon occurs in many other species of Unctnula. In U. salicts 
it can be seen on examining perfectly ripe examples that many of 
the perithecia have become turned over, so that the apices of the 
appendages rest against the surface of the leaf. This can be well 
seen in the specimens in De Thiim. Fung. austr. 655 (in herb. 
Kew). In a few instances, I have observed, in herbarium speci- 
mens, that the perithecia, through the mucilaginous degeneration 
of their appendages, have become actually fixed in this position to 
the leaf. It is easy to produce the same result artificially. A 
leaf after having been placed in water for a few minutes, and then 
freed from the superficial moisture, was laid on the surface of a 
leaf which bore numerous ripe perithecia of U. sa/cis—an example 
being chosen in which the appendages of the perithecia were spread- 
ing upwards. After a few hours, the superposed leaf was exam- 
ined, and it was then found that several reversed perithecia were 
adhering by their appendages to its surface. These perithecia 
required a slight amount of force to be detached. Perithecia of 
U. salicis were placed upside down on damp leaves of Hedera 
Helix, and it was found after a short time that these had adhered 
to it by their appendages. In U. macrospora, U. prunastri, and 
U. Clintonit the same reattachment of the perithecia in a reversed 
position can be observed. An ivy-leaf, was laid upon a leaf of 
Tilia Americana bearing numerous perithecia of U. Ciimtoni in 
which the appendages were spreading upwards. After a few hours 
perithecia reversed and fixed by their appendages were found on 
the ivy-leaf. 
On account of their large size, the reattachment of tle perithecia 
