THE SPORES OF LICHENS. 121 
De Notaris in 1846, from which period Krempelhuber dates 
the modern period of Lichenology, fully inaugurated the 
new method, and established it on a solid foundation. He 
pointed out the unity of the spore-type in many natural 
genera, and declared that species in which the spores pre- 
sented important differences could not be grouped together. 
But the results of his labors do not appear to have been com- 
bined into a general system. Norman, in Norway, 1852, 
Massalongo, in Italy, 1852, and Koerber in Germany, 1854— 
1859, continued his work, and based their systems to a greater 
or less degree, on spore characters, while the younger Fries, 
Trevisan, Stitzenberger and others have labored successfully 
in the same field, and made important contributions to this 
department. No description of a lichen is now considered 
adequate which does not give an account of the spores, when 
they are to be found. 
The Italian school, however, has attributed too great im- 
portance to minor distinctions in the size of spores, their 
septation, and number in the spore-case, attaching great im- 
portance to micrometric measurements, and lonbr.: increas- 
ing the species and genera to a most unwarrantable degree, 
e not unfrequently violating natural affinities, answering 
no useful end and tending rather to create confusion than 
to advance true science. A few instances may serve to illus- 
trate this. Pyrenula nitida Scher. is a very common bark 
lichen, and subject to but slight variation. The average 
length of the spores is from .018 to .022 millimetre; but 
specimens occur, which cannot be separated from it, in which 
they measure constantly from .030 to .038. Arthonia 
velata Nyl. is another instance in which the spores in some 
specimens are constantly nearly twice as large as in others. 
The spores of Sagedia chlorotica Ach. are described in 
the European forms as constantly 4-blastish, measuring from 
.018 to .023. Here they are usually from 4 to 6-blastish, 
and measure from .025 to .047, and it is only recently that 
I have found specimens with constantly 4-blastish spores, a 
AMER. NATURALIST, VOL. IV. 91 
