176 
THE FLOEIST AND POMOLOGIST. 
[ August, 
a fine white pulverulent stratum. To get a really good view of this damaging 
fungus, it is necessary to cut an almost inconceivably thin transverse slice out of 
the lamina of the leaf. It is not every one who can perform this feat to per¬ 
fection, but practice and perseverance at length overcome all difiSculties. At c c 
is shown one of these extremely thin transverse slices from a part of the leaf where 
there is no disease, and d d shows a similar section, but cut out of the thick, 
leathery blister, with the fungus in situ on the top. o c and D d show respec¬ 
tively the thickness of the diseased and healthy portions of leaf, and this shows 
how very small the fungus is in comparison with the thickness of the leaf. 
The section from the uncontaminated quarter of the leaf needs no comment, 
but it will be seen at a glance that the whole of the cells in the diseased portion 
are morbidly enlarged in size and materially increased in number. If our figure 
had been coloured, the cells would all be green in the healthy slice, and corroded 
to crimson in the diseased one. The fungus is clearly capable of exciting a 
morbid growth, both in the number and size of the component parts of the leaf. 
The Ascomyces belongs to the same order with the large and delicious Morel, 
and the various species of Peziza^ some members of. the order being amongst the 
largest of known fungi, whilst Ascomyces is amongst the smallest, and, says Mr. 
Berkeley, ‘‘the lowest form to which the Ascomycetes can be reduced.” The 
white pulverulent stratum, when enlarged to 200 diameters, is seen as shown at 
E, and consists of a basement of threads, from which arise numerous sacs (asci), 
intermixed with necklace-like organisms, which latter, when broken up, doubtless 
form a second form of fruit. The true sporidia are contained in the asci, eight in 
a sac, and this latter membranous receptacle at a certain moment of excitement 
opens a sort of mouth at the top, and discharges the sporidia into the air, as is 
show in the engraving. The sporidia (= spores, or analogues of seeds) are seen 
to better advantage at f, where they are still further enlarged to 800 diameters, 
to better show the one, two, or three nuclei with which they are furnished, and 
which remind the botanist of a similar structure in the sporidia of the genus 
Propolis. There are various other species of Ascomyces met with in this countiy, 
on the leaves of the Pear, Walnut, &c., and one on the Continent, with which 
we are acquainted, which grows upon the leaves and fruit of the Plum. The latter 
we have not at present seen recorded from this country. 
The foregoing is the substance of a paper by Mr. W. G. Smith, in the 
Gardeners^ Chronicle., whence the accompanying woodcut is also derived. Whether 
or not the disease is to be directly attributed to the action of the fungus, or 
whether to ungenial climatal conditions favourable to the development of the 
fungus, there can be no doubt it is usually present. As a remedial measure, the 
affected leaves should be removed, and at once burnt, so as to destroy the germs 
of the fungus, as should also be done with that more formidable enemy, the Potato 
fungus. If attacked by the disease, the haulm should be removed at the earliest 
moment it can be spared—in the case of a virulent attack, it should be cut away 
at once—and as soon as possible purified by fire.— Ed. 
