326 THE STUDY OF MINUTE FUNGI. 
‘three or four one-thousandths of an inch as they appear through 
the camera. At each of these points draw a line perpendicular to 
the base. The most convenient length for these lines is 24 inches. 
Now divide these lines into ten equal parts, by lines ruled parallel. 
to the base line, and then draw a line diagonally from one of the 
zoo inch marks on the base line to the next 5/55 inch mark in 
the tenth line above. You will thus have constructed a diagonal 
scale which will measure to the ten-thousandth of an inch. To 
use it, you lay it on the stage beside the object, and view it with 
one eye and the object with the other. You will with a very little 
practice see the object projected on the card and can read off its 
length at once. ' 
On measuring the spores of your specimen, you find that they 
are .0004 of an inch long. The spores of all the species in this 
division of the Valsæ are shorter than this, with the exception of 
Valsa stellulata Fr. Fr. stands for Fries, a great Swedish mycolo- 
gist who named and described this species and this is his descrip- 
n. 
«9. stellulata.—Subrotunda, immersa, stromata albo circum- 
scripto, ostiolis ovato globosis, brevibus radiato stellatis” ..- 
The “ Systema Mycologicum” of Fries from which the above de- 
scription is taken, was published in 1822, and, of course, at that 
time there was no microscope at his command by which he could 
define the fruit. The first description of the spores of this spe- 
cies was given by De Notaris, in 1853, in the Memoirs of the 
Academy of Science in Turin. : 
But the mere giving a name to our fungus, or finding out what 
name somebody else has given to it, amounts to very little, except 
as giving the same sort of mental exercise and amusement, as the 
putting together a puzzle of any kind would do. What we want 
to know, is, how did the Valsa get there under the bark? What 
is its life history, and what is its use or purpose, if it has any ? 
And the first question of all to occur to you, if you have become @ 
little impatient of the very minute points by which one of the s0- 
called species differs from another is, how do you know that these 
points indicate specific differences? In other words why do you 
practically assert that the fungus with spores exactly like, but 
with spores the one ten-thousandth of an inch shorter than an- 
other fungus, may not be merely a stunted specimen of the latter? 
To the latter query I must reply, that at present we have no satis- 
