(143) 
Reckoning roughly those added since the publication of the estimates 
-of Nylander (Syn.) the whole number of probable species of Lecideacei, 
as here taken, known to science, may be set down as not very far from 
about a third of the whole number of species of Lichens. In the spores 
the colourless type predominates, at least as largely as in Parmeliacei. 
Fam. 1.—CLADONIEI (Zenk., Koerb.) Th. Fr. 
Thallus duplex: horizontalis, squamulosus 1. granulosus, nunc 
evanidus, et verticalis caulescens, dein suffruticulosus (podetia). 
Considering, with Fries, the Lecideacei as a series of evolution running 
parallel with Parmeliacei, it is evident at once that the present family 
corresponds with the Usneei of the latter tribe. It is distinguished how- 
ever by the remarkable character that the erect thallus of the Cladoniet 
springs from a horizontal one; which, whether with Koerber (Syst. p. 9) 
we attempt to distinguish it from the true thallus, as a certain develop- 
ment of the hypothallus (protothallus, Koerb.) or the rather assume that 
it corresponds, in all respects, with the thallus of the Lecideei, is equally 
interesting, in its relation to the other. This horizontal thallus, especially 
developed in Cladonia, is conspicuous also in Pilophorus fibula, and 
scarcely less so in Stereocaulon condensatum, and S. cereolus ; but dis- 
appears, or is even obsolete from the first, in the more fruticulose forms 
of all the genera. 
In the line of analogy afforded by the spores, Stereocaulon answers 
more particularly to Roccella, of the Usneei; Pilophorus may be com- 
pared perhaps rather with Usnea; and Cladonia with Dactylina and 
Evernia. 
The Cladoniei constitute about one-fifth of the present Tribe. 
XXXVII.—STEREOCAULON, Schreb. 
Schreb. Gen. Pl. p.768. Ach. L.U.p.113. Fr. UL. E. p. 200. Tuckerm. 
Syn. N. E. p. 44 (sect. 2 excl.) Mass. Mem. p.74. Koerb. Syst. p. 10. 
Nyl. Prodr.; Syn. 1, p. 280, t.7,f. 7-81. Th. Fr. Monogr. Ster. et 
Piloph. p. 9-67, & tabb. 1, f. 1-3, 2, 3, 4, f.1; Beitr. z, Kenntn. der 
Cephalod., in Flora, 1866, p. 18. Stizenb. Beitr. 1. c. p. 167. Patel- 
lari sect., Wallr. Fl. Crypt. Germ. 1, p. 438. 
Structuram exposuerunt Tulasne, Mém. sur les Lich. pp. 26, 173; 
Schwendener, Untersuch. in Naeg. Beitr. 2, p. 173, t. 7, f. 10-11; Die 
Algentypen d. Flechtengonid. pp. 16, 27, 33. 
Apothecia patelleformia, excipulo proprio, dein cephaloidea, 
solida. Spore fusiformes 1. aciculares, 4-pluriloculares, incolores. 
Spermatia ex oblongo sepius bacillaria 1. acicularia; sterigmatibus 
