Apr.-sept., 1915 Illustrations XI 



Page 

 the disintegration of the spore walls. Fig. 3 . — A semidiagrammatic drawing 

 of a section through a very young sorus, showing the infecting plasmodium 

 as it pushes down between the cells. Fig. 4. — An infecting plasmodium. 

 Fig. 5. — A potato cell becoming infected by a plasmodium of S. stibterranea. 

 Fig. 6. — A Plasmodium closely applied to the host nucleus. Fig. 7. — A 

 small portion of a plasmodium. Fig. 8. — Portion of a plasmodium within 

 an infected cell, showing the dense c>i;oplasm around the nuclei and the 

 clearer region between them. Fig. 9. — A plasmodium pushing down be- 

 tween mature cells and causing secondary infection 278 



Plate XL. Spongospora subterranea: Vertical section through a very young 



sorus, showing the plasmodium as it pushes down between the cells 278 



Plats XLI. Spongospora subterranea: A vertical section through the edge of a 



3^oung sorus, showing the intercellular spaces beneath the raised epidermis. 278 



Plate XLII. Spongospora subterranea: Vertical section through the edge of a 

 young sorus, showing the plasmodia in the potato cells and the intercellular 

 spaces above which were previously occupied by the infecting plasmodium . . 278 



Plate XLIII. Spongospora subterranea: Fig. i. — A vertical section through a 

 sonis soon after it has broken through the epidermis. Fig. 2. — A living 

 Plasmodium obtained from a cultture of germinating spore balls 278 



Rheosporangium Aphanidermatum, a New Genus and Species of Fungus 

 Parasitic on Sugar Beets and Radishes 



Plate XLIV. Rheosporanghnn aphanidermaiurn : Fig. i. — Cleavage of the spo- 

 rangium into zoospores within the wall of the presporangium. Fig. 2,3,4, 

 5, 8, 9, II. — Nuclear divisions in the mycelium. Fig. 6. — Portion of pre- 

 sporangium showing rupture at tip and the initial stage of sporangium 

 egress. Fig. 7. — Maturing presporangium. Fig. 10. — Later stage of spo- 

 rangium egress from a branch of the presporangium. Fig. 12. — Vegetative 

 mycelium; living. Fig. 13. — Section of nearly mature presporangium, 

 showing development of large vacuoles 292 



Plate XLV. Rheosporangium aphanidermatum: Fig. 1,2,3,4, 5. — Sections of 

 sporangia showing various stages of cleavage into zoospores. Figure 3 shows 

 mitochondria and, at the periphery, fragments of cilia. Fig. 6. — Segment of 

 mycelium showing accumulation of cytoplasm characteristic of old aquatic 

 cultures; living material. Fig. 7. — Oospore within the old oogonial wall, 

 antheridia wall attached. Fig. 8. — Young oogonium and antheridium not 

 yet cut off from the parent hyphse 292 



Plate XLVI. Rheosporangium aphanidermatum: Fig. i. — Section of presporan- 

 gium showing nuclei and mitochondria. Fig. 2. — Section of zoospore 

 showing mitochondria. Fig. 3. — Advanced stage of zoospore germination. 

 Fig. 4. — Section of zoospore showing position of central vacuole and nu- 

 cleus. Fig. 5. — Stages in tha preparation of the fused nucleus of the oospore 

 for division. Fig. 6. — Zoospore showing position of sinus in side. Fig. 7. — 

 Section through zoospore showing blepharoplast and sinus. Fig. 8. — Myce- 

 lium showing nucleus and mitochondria. Fig. 9, 10. — Sections of zoospores 

 showing blepharoplast and attachment of cilia. Fig. 11. — Zoospore show- 

 ing orientation of the various structures. Fig. 12. — Maturing oospore show- 

 ing fused nucleus, large central food body, and the wall, which is un- 

 usually deeply contoured. Fig. 13, 14, 15, 16, 17. — Stages in zoospore 

 germination. Fig. iS. — Section of matxiring oospore. Fig. 19, 20. — Matur- 

 ing oospores showing usual type of wall and the fused nucleus in prepara- 

 tion for division 292 



