120 Certain Fungi Parasitic on Plants. 
of insect life, and has led to the belief that it was produced by 
them. 
In answer to a communication of mine, Professor C. H. Peck, 
botanist, of Albany, New York, informs me that he has found sacs 
(asci) filled with spores within the perithecia of black-knot, and has 
furnished me with a sketch of the sac as seen by him (see U, 
Plate XCVI.). T represents a highly magnified view of the true 
spore of this form of Spliseria. After several fruitless dissections, 
in search of the sporidia, I found them ultimately floating among 
the crushed cells on the glass slide. They are almost colourless, 
with a slight tinge of green, and are smaller than the spores of the 
flocci. Although I have not seen these spores in sacs, I think it 
likely that the drawing U is correct, and I can testify to the accuracy 
of that of the spore T. 
In the growth of black-knot the perithecia crowd each other so 
much, that their original shape is changed in a variety of ways, 
but in the main I have frequently found well-defined forms, as 
represented. 
Having recently received from a gentleman of New Jersey, 
Mr. Abram McMurtrie, some excellent specimens of black-knot 
taken from plum and cherry trees of different ages, I resumed my 
investigations of that disease with very satisfactory results. A 
portion of the fungus being removed from a specimen of the black- 
knot which had grown on a plum tree about seven years old, and 
being submitted to an examination by the microscope, at a very low 
power, exhibited forms of fruit (perithecia) as seen at 8, Plate XCVI. 
When viewed in section by a higher power, it appears as at 9 ; and 
in top view as at 10, showing an indentation in each perithecium. 
When they are imperfect they appear as at 11. 
If a perfect specimen, as seen at 9 or 10, is submitted to the 
action of nitro-muriatic acid for about thirty .minutes, a slight 
decomposition of the acid takes place, indicating that the resinous 
or oily matter of the perithecium becomes oxidized. These strong 
mineral acids have no destructive action on the organic structure of 
the perithecium, although they have the property of bleaching it in 
some degree, thus rendering it translucent, and making its cellular 
structure visible. If ammonia is added in drops to the specimens, 
after having been treated with acids, their albuminoids become pliable. 
This process is especially valuable when applied to matured and dry 
specimens ; 6, Plate XCVI., represents a very highly magnified 
specimen of a perithecium, a part of which is in section and repre- 
sents the internal arrangement of the asci and sporidia in them. 
From my recent experiments on black-knot I am now able to de- 
monstrate its structure. If a perfect perithecium which has been 
treated with acid and ammonia, as previously described, is gently 
bruised on a microscopic glass slide, by any of the well-known 
