Fig. 7. A fragment of the capillitium, x 240. Fig. 7 _a_. A single spore of the same species, x 1400. See also Plate XII., Fig. 3. [Illustration: PLATE X] EXPLANATION OF PLATE XI _Comatricha nigra_ Pers., p. 178. Fig. 1. A group of sporangia, x 10. Fig. 2. A single sporangium as in section, x 60. Fig. 3. A single spore, x 1600. _Stemonitis confluens_ Ell. & Cke., p. 158. Fig. 4. A group of sporangia, x 10. Fig. 4 _a_. A thread of capillitium with adhering disk, x 30. Fig. 5. A spore of the same, x 2000. _Stemonitis webberi_ Rex, p. 163. Fig. 6. A group of sporangia, x 4. Fig. 7. A single sporangium as in section, x 40. Fig. 8. A single spore, same species, x 1250. _Comatricha suksdorfii_ Ell. & Ev., p. 178. Fig. 9. A group of sporangia, x 4. Fig. 10. A bit of the capillitium, x 60. Fig. 11. A single spore, x 1600. _Comatricha caespitosa_ Sturg., p. 172. Fig. 12. A cluster of sporangia, x 4. Fig. 13. The capillitium highly magnified. Fig. 14. A single spore, x 1600. [Illustration: PLATE XI] EXPLANATION OF PLATE XII _Lindbladia effusa_ (Ehr.) Rost., p. 204. Fig. 1. Fructification, natural size. Fig. 2. Portion of same in section, x 3. _Reticularia lycoperdon_ Bull., p. 210. Fig. 3. Residual capillitial structure, the spores blown away; about natural size. _Enteridium splendens_ Morg., p. 211. Fig. 4. Fructification, a large one, natural size. Fig. 5. Same in section, x 3. _Arcyria ferruginea_ Sauter, p. 253. Fig. 6. Three sporangia, magnified about 10 times. Fig. 6 _a_. A single spore, magnified. Fig. 6 _b_. Capillitial thread. _Licea variabilis_ Schrad., p. 200. Fig. 7. Sporangia, magnified about 6 times. Fig. 8. Spore, magnified to show surface characters. _Tubifera casparyi_ (Rost.) Macbr., p. 207. Fig. 9. A group of sporangia; shows the pseudo-columellae; x about 5. _Licea biforis_ Morg., p. 201. Fig. 10. Sporangia dehiscent, magnified about 10 times. _Orcadella operculata_ Wing., p. 203. Fig. 11. Sporangia, magnified about 30 times. _Cribraria argillacea_ Pers., p. 218. Fig. 12. Sporangia, magnified about 10 times. Fig. 13. A single sporangium, x about 40. See also Plate XVII., Fig. 1. _Tubifera ferruginosa_ (Batsch) Macbr., p. 206. Fig. 14. Sporangia magnified to show apiculate tops. Cf. _Comatricha ellisii_ Morg., p. 184. Fig. 15. Sporangium, x 40. Fig. 15 _a_. A single spore, x 1000. _Comatricha pulchella_ (Bab.) Rost, p. 183; vid. p. 284. Fig. 16. Sporangium, x 20. Fig. 16 _a_. A single spore, x 1000. _Comatricha subcaespitosa_ Peck, p. 185. Fig. 17. Sporangium, x 20. Fig. 17 _a_. A single spore, x 1000. _Comatricha gracilis_ Wingate, p. 183. Fig. 18. Sporangium, x 20. Fig. 18 _a_. A single spore, x 1000. [Illustration: PLATE XII] EXPLANATION OF PLATE XIII _Heterotrichia gabriellae_ Mass., p. 257. Fig. 1. A group of sporangia, one expanded, the others empty, x 15. Fig. 1 _a_. Capillitium of the species, x 600. _Calonema aureum_ Morg., p. 266.