PTERIDOPHYTA. 211 
the small fibro-vascular bundle in the midrib. Study the epidermic 
which contains numerous breathing-pores. 
(8) Carefully dissect out from the fruiting cone of a Little Club- 
moss several spore-cases, the lower ones with four large spores, the 
upper with many small spores. Examine in like manner a cone of 
Lycopodium, in which but one kind of spore will be found. 
(c) Search the borders of lakes, ponds, ditches, and slow streams 
for Quillworts, which may be at once distinguished from grasses, 
rushes, etc., by the spore-cases on the bases of the leaves. Although 
they are rarely collected, they may doubtless be found in almost 
every locality in the United States. 
(d) Collect pteridophytes in fruit and dry them under pressure, 
afterwards gluing them to sheets of heavy white pape for herbarium 
specimens. The best size is 42 centimetres (164 inches) long, by 
30 centimetres (114 inches); this is the size adopted by the botanists of 
this country and used in the large herbariums. 
(e) For the identification of the species of pteridophytes of this 
country the student may profitably use ‘“‘Our Native Ferns and 
their Allies,” by L. M. Underwood. 
