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Nylander’s view of the difference in the two species. H. Willey and W. W. 
Calkins both record from Illinois, but we have no means of knowing whether 
the two species were differentiated or not. Cladonia bacillaris and Cla- 
donia macilenta seem to be scarcely distinct, but herbarium specimens indi- 
cate that the latter plant is more robust and more commonly branched. The 
spore arrangement is not easy to make out and is not always to be 
depended upon, as the spores may be obliquely arranged in certain asci and 
irregularly in others of the same plant. Tuckerman recognized only Cla- 
donia macilenta , which he gave a wide North American distribution. Judg- 
ment as to whether Cladonia bacillaris and Cladonia macilenta are distinct 
species must finally be based upon wide study of specimens by the statistical 
method, taking account of centres and ranges of variation and degree of isola- 
tion of various forms encountered. For the present, we can find no better way 
than to attempt to follow Dr. Wainio, who records the present species from all 
the grand divisions. It is reasonable to suppose that chemical tests may have 
some value in differentiating these two closely related species. 
Dr. Wainio gives five forms, of which only the first and most common 
one has been noticed in North America. This we would regard as the 
species. 
Cladonia didyma (Fee) Wainio Mon. Clad. Univ. 1:137. 1887. Primary 
thallus disappearing or rarely persistent, composed of minute or medium 
sized, laciniate or incised crenate squamules, which are 0.5-3 mm. long and 
0.12-0. 15 mm. in diameter: somewhat involute or nearly flat, scattered or clus- 
tered; without soredia, sea green above, varying toward olivaceous or rarely 
toward whitish, below whitish, or yellowish toward the base of the squam- 
ules. Podetia arising from the surface of the primary thallus; short or some- 
what elongated, 1-45 mm. in length and o 5-3 mm. in diameter; cylindrical 
and without cups; simple or with erect or divergent branches: erect, clus- 
tered or subsolitary: decorticate, or more or less corticate at the base, whit- 
ish-sea-green, varying toward whitish or brownish: squamules for most part 
toward the base or absent; squamules, verrucae, granules or soredia minute. 
Apothecia medium sized, or rather small, 0.3-2. 5 mm. in diameter, solitary 
or more or less clustered; convex and immarginate, scarlet. Hypothecium 
pale or cloudy. Hymenium deep red above and pale below. Paraphyses 
simple, more slighly thickened toward the apex. Asci cylindrico-clavate. 
Spores irregularly arranged. 
On old trunks, earth or rocks. Examined by the writer from Virginia 
(A. B. Seymour), Louisiana (A. B Langlois), Florida (W. W. Calkins). The 
specimens of Calkins and Langlois were submitted to Dr. Wainio. Cladonia 
pulchella, to which these men had referred their specimens, is a synonym. 
Wainio cites the species from Massachusetts, Alabama, Mexico, Guadeloupe, 
St. Domingo, Cuba and Martinique. Dr. J. W. Eckfeldt referred one of A. 
C. Waghorne’s plants from Newfoundland here, otherwise our distribution is 
confined to the United States and the islands. Common also in South Amer- 
ica and known in Asia, Africa and Australia. 
Dr. Wainio referred the specimens submitted to him to his first form, 
Muscigena (Nyl.) Wainio. Mon. Clad. Univ. 1:141. 1887, which is the com- 
mon form which may well stand for the species, the only one thus far noted 
in North America. Miami University, Oxford, Ohio. 
