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they might appear perfectly hyaline. These areas have been called pale. 
Then in some other lichens similar sections are somewhat denser in these 
areas so that in sections of ordinary thinkness there is a darkish cast that 
really appears like the color of clouds. Then plainly enough, a section will 
tend toward a pale appearance if thin, and is more likely to be cloudy if 
thick. And in the interpretations of these and all other colors seen in sec- 
tions, some allowance must be made for the thickness of the section. Of all 
the diagnostic characters given in descriptions, perhaps those regarding the 
paraphyses have least value. The common statement is about thus, para- 
physes simple or rarely branched, commonly enlarged and brownish toward 
the apex. This answers for the great majority of lichens with little modifi- 
cation but when the statement varies considerably from this form, the para- 
physes are of more consequence in determination. Also, it should be said 
that in measurements, macroscopic and microscopic, there is usually no spe- 
cial effort made to reach the rarest extremes in sizes. So the student need 
not be surprised at finding occasionally larger or smaller measurements than 
those given. However, the extreme sizes must not vary greatly from those 
of the manual used. 
The Herbarium. 
Specimens once determined should be carefully dried so as to avoid 
moulding, and the larger ones are to be pressed in the same way that higher 
plants are pressed, placing the specimens in the press, not soaked with 
water, but just damp enough to press well. The crustose and closely adnate 
foliose species seldom need pressing. Earth containing small foliose or 
•crustose species must be saturated with mucilage, which will keep it from 
crumbling in the herbarium and destroying the specimens. All but the rock 
specimens keep well in the ordinary herbarium envelopes, and even they are 
often kept in the envelopes also. But if one is not very careful not to get 
large pieces of rock, it is usually necessary to resort to stronger and larger 
envelopes or pasteboard boxes for these rock lichens. Delicate specimens as 
Caliciums, and members of some other genera had better be glued to the 
bottom of small boxes in such a manner that the delicate lichens will be out 
of contact with anything else than the substratum on which they grew. The 
envelopes may be mounted on ordinary herbarium paper, but brown paper 
is very commonly used by the lichenists of Europe, both for envelopes and 
mounting paper. This paper does not show dirt as does the white paper. 
Many paste all specimens to paper if removed from the substratum ; but if 
this is done, part of the material must be placed ventral side upward so that 
both sides of the thallus may be seen. This method helps to prevent break- 
ing the brittle thalli, but interferes somewhat with the study of the speci- 
mens. All specimens in the herbarium must contain careful data such as 
those suggested to be taken in the field. Finally, it is not possible that a 
short paper should contain all the suggestions that are valuable in the col- 
lecting and study of lichens, but it is hoped that those given may enable the 
members of the chapter and others to work somewhat intelligently, while 
gaining that experience which is more valuable than any directions that can 
be given. Grinnell, Iowa. 
