Fig. 11 _a_. Vertical section, after Rost., x 500. _Physarum compressum_ Schw., p. 80. Fig. 12. Sporangium, x 20, to show dehiscence. _Didymium anomalum_ Sturg., p. 127. Fig. 13. Plasmodiocarps, about natural size. Fig. 13 _a_. Diagrammatic vertical section, etc., to show the calciferous pillars distinguishing the species, x 200. Fig. 14. Calcic crystal--enlarged. _Physarum sinuosum_ (Bull.) Weinm., p. 52. Fig. 15. Plasmodiocarps passing to sporangia, x 5. Cf. Plate VIII., 6 and 6 _a_. _Physarum bitectum_ List., p. 53. Fig. 16. Plasmodiocarps as in 15, showing transitional phases, x 10. [Illustration: PLATE XIX] EXPLANATION OF PLATE XX _Badhamia iowensis_ n. s., p. 36. Fig. 1. Sporangia several presentations, x 15. Fig. 1 _a_. Capillitium, x 200. Fig. 1 _b_. Single spore, x 500. _Physarum mortoni_ n. s., p. 58. Fig. 2. A group of sporangia, x 20. Fig. 2 _a_. Capillitium, x 200. _Physarum discoidale_ n. s., p. 74. Fig. 3. A group of sporangia, x 10. Fig. 3 _a_. A single spore, x 800. _Didymium annulatum_ n. s., p. 125. Fig. 4. Group of sporangia, x 15. Fig. 4 _a_. Capillitium and spores, x 200. _Oligonema brevifilum_ Peck, p. 280. Fig. 5. Capillitium, x 800. Fig. 5 _a_. The same. Fig. 12 _b_. A single spore, x 800. _Amaurochaete tubulina_ (Alb. & Schw.) Macbr., p. 150. Fig. 6. Capillitium and spores, x 200. Fig. 6 _a_. Spore, x 1200. _Physarum brunneolum_ (Phill.) Mass., p. 58. Fig. 7. Group of sporangia. Fig. 7 _a_. The same, mature, dehiscence beginning, x 10. Fig. 7 _b_. A single spore, x 800. _Stemonitis uvifera_ n. s., p. 161. Fig. 8. Colony, natural size. Fig. 8 _a_. Capillitium and spore-clusters, x 30. Fig. 8 _b_. Single spore-cluster, x 600. Fig. 8 _c_. Spore, x 1000. _Stemonitis trechispora_ Berk., p. 160. Fig. 9. Fructification--natural size. Fig. 9 _a_. Capillitium, branch and threads, x 20--the spores enlarged. Fig. 9 _b_. Netted spore, x 1000. Masking as an amaurochete; _A. trechispora_ perhaps; compare 11, etc., below. _Stemonitis flavogenita_ Jahn, p. 169. Fig. 10. A group of sporangia, x 3. Fig. 10 _a_. Capillitium showing columella-tip, x 50. Fig. 10 _b_. Spore, x 1200. _Stemonitis trechispora_ (Berk.) Torr., p. 159. Fig. 11. A group of sporangia, x 3. Fig. 11 _a_. Diagram of a single sporangium, a less rudimentary specimen, x 40. Fig. 11 _b_. Capillitium enlarged to show branching columella, x 40. Fig. 11 _c_. A single spore, x 1200. _Arcyria pomiformis_ (Leers) Rost., p. 255. Fig. 12. A globose colony of sporangia, x 10; var. _conglobosa_. Fig. 12 _b_. See under 5, above. [Illustration: PLATE XX] EXPLANATION OF PLATE XXI Brefeldia maxima (Fr.) Rost., p. 154. A typical, beautiful aethalium, about natural size. [Illustration: PLATE XXI] EXPLANATION OF PLATE XXII _Brefeldia maxima_ Rost., p. 154. Fig. 1. Plasmodium active; climbing the stump. Fig. 2. Same plasmodium urgent; moving at the rate of 2 cm. per hour.