266 
NOTES AND MEMORANDA. 
sitic fungus, Xyloma acerinum, which constitutes a special type of 
affection. This is only an imperfect and summer form ; when the 
leaves fall in the autumn a further growth takes place in the spots ; 
the plant acquires theca© and becomes Hhytisma acerinum. 
In the same locality the spots appear every year. Is the parasite 
perennial as some Uredin^ [^cidium Euphorhice sylvaticce and a great 
number of Pucciniae) ? Is it annual like the Boestelia and the greater 
part of the ^xidia f Sown in one point, does it spread through the 
plant like Endophyllum Sempervivi, Peronospora Papaveris, &c. ? 
Some very young shoots of maple were placed in several flower- 
pots ; two had each eight, and were a reserve, the others, each con- 
taining four, were used for experimenting. 
On the 1st April, 1874, some mature spots of Bliytisma were cut 
into narrow strips like tobacco, and wetted, and then in small heaps 
placed in contact with the young maples. All parts are not equally 
fit for the introduction of the parasite : TJstilago carho penetrates by 
the collum, Crystopus candidus by the cotyledons. Direct anatomical 
investigation of the mode of introduction of the germs is rendered 
extremely difficult by the form of the spores, which are very elongated, 
by their diameter and that of the germinal filaments, which are very 
slender, but above all by the irregularity of the germination. 
Four experiments were made to determine the mode of pene- 
tration. The small heap was placed : — 
A. Pound the collum at the level of the soil. 
B. In the fold of a cotyledon rolled up and maintained in that 
position by a pin. Each of the two pots was covered over with 
another soaked with water to prevent desiccation, vapour, and the 
removal of the spores by the wind. 
None of the leaves showed any Bliytisma either in 1874 or the 
following years. 
C. In the cleft of two cotyledons, on the leaves of the terminal 
bud, at that time little developed. 
D. Between the leaves of the terminal bud already raised by the 
stem. The cotyledons were smeared with suet down to their base in 
order to isolate them; they soon withered and fell. The plants, 
although vigorous at the beginning, remained more slender than the 
others. 
In the two latter cases the Bliytisma appeared after two and a half 
months. The spots were at first white and greenish grey, then turned 
black in places, and finally over their whole surface. In the middle 
of July the spot was completely formed. 
The plants were shown to M. Brongniart, M. Duchartre, M. Eoze, 
and several other botanists. In the autumn all the leaves which fell 
were collected. The following year, and since, the parasite did not 
show itself ; it appears therefore to be annual. It seems also to be 
very narrowly localized. In the plants experimented on, the lower 
leaves, the only ones then developed, were alone spotted ; the spots 
were all in the same state ; the mycelium did not spread. 
In 1876 I attempted to mark out on the leaves (not very young, 
but already large) some lines and crosses by means of the Bliytisma. 
