260 MR. F. CURREY ON THE FRUCTIFICATION OF COMPOUND SPHJERLE. 
Micrometric measurements of length should always be given. The size of sporidia is 
of course subject to variations dependent upon the circumstances of growth of the plant 
producing them, but as a general rule these variations take place Within narrow limits. It 
not unfrequently happens that the sporidia increase in size after their escape from the 
ascus, so that measurements taken from specimens in which the asci have disappeared, 
will often be found to exceed the mean lengths of the sporidia when measured in the 
interior of the ascus. 
I will conclude these introductory observations with a caution, superfluous to practised | 
microscopists, but which may not be without its use to others who may consult the 
measurements here given; viz., that it is indispensable for correctness of observation to 
ascertain with accuracy the magnifying power of their object-glasses. Opticians, as is 
well known, always furnish tables giving estimates of the magnifying powers, but the 
tables are not (nor do the opticians profess that they are) minutely accurate. They ex- 
press, in fact, the magnifying power aimed at, not that actually attained; and it will be 
found in practice that in object-glasses of the same focal length, no two will magnify 
exactly the same number of diameters. In the measurement of objects so minute as the 
sporidia of many of the Spherie, great accuracy is indispensable for avoiding erroneous 
conclusions. I need hardly add that the correct determination of the value of the micro- 
meter divisions is equally necessary. The arrangement of the “ Sphæriæ composite” 
according to the * Systema Mycologicum’ is subjoined, with the essential characters of the 
genus, sections and divisions. 
SPHÆRIA, Hall. 
CHAR.—Perithecia rounded, entire, perforated at the apex. Asci mixed with paraphyses, convergent, 
deliquescent. Sporidia various. 
A. COMPOSITÆ. 
SECTION I. PERIPHERICZ.—Perithecia more or less divergent, situated in the periphery of the 
stroma; ostiola even, destitute of a neck. 
Div. 1. Corpycers.—Stroma club-shaped, erect, simple or branched, stipitate. 
Div. 2. Poronta.—Siroma marginate, cupshaped, open. Perithecia ovate, situated in the disk of 
the cup only, destitute of a neck ; ostiola even and prominent. x 
Div. 3. PuLvinatæ.—sStroma sessile, convex, more or less hemispherical, immarginate. Perithecia 
in the periphery of the stroma. 
Div. 4. Connat#.—Stroma widely effused, indeterminate, immarginate, plane, surrounding the 
perithecia, or arising from their confluence. Perithecia destitute of a neck, immersed in the 
stroma, or protruding. 
SECTION II. Hyroruericæ.—Perithecia vertical, immersed, covered with the stroma, and having an 
attenuated neck. : 
Div. 5. GueBosa.—Stroma more or less effused, determinate, glebose, distinct from the matrix, 
at length rigid and brittle. Perithecia ovate, large, at first buried and mouthless, at length 
attenuated into a short neck ; ostiola even. 
Div. 6. Licnosæ.—Stroma effused, thin, plane, more or less determinate, connate with the matrix; 
circumscribed with a black line. Perithecia sunk down to the bottom of the stroma, crowded, 
with prominent ostiola. 
Div. 7. VERSATILES.— Sfroma immersed, at length emergent, determinate, but confluent with the 
