144 THE SAPKOLEGlSriACE^ OF THE UNITED STATES, 



Explanation or Plates. 

 Piatt XIV. 



Fig. 1 . A fly attacked by Saprolegvia sp. x 2. 



Fig. 3. Rhizoids of ,8. mixta, gi"ving rise to an exteinal hypha, h. X 130. 



Fig. 3. Cut-off ends of hyphse of ;Sap7-o%«m sp. repaired by the formation of a cellulose •wall. X 200. 



Fig. 4. Protoplasm and nuclei of a portion of an hypha of ^. racemosa. X 940. 



Picric-acid-Haematoxylin specimen ; the protoplasm somewhat retracted from the walls by the action of the acid. 

 Fig. 5. Nuclear division in an hypha of A. apiculata. X 1400. 



a. The nucleus, showing chromatin-mass, nuclear membrane, and the intermediate space. 



b. The chromatin -mass has elongated with the rest of the nucleus. 



c. The chromatin mass is dividing. 



d. The nuclear membrane is formed between the daughter-nuclei, which have not yet separated. Corrosive-subli- 



mate-Haematoxylin preparation. 



Fig. 6. A bit of i. lactevs, showing monopodial branching and two cellulin granules, c. X 540. 



Fig. 7. Two stages in the develoiment of thez( ospores of J. J«?mca7!a, showing only the base and tip of the spo- 

 rangium. X 330. 



a. The first separation fairly marked, at 11.10 a.m. 



b. The "homogeneous" stage, at 11.23. 



Fig. 8. A sporangium of /S'apro?<'g'r!»a sp., with zoospores in the act of escaping, some already out, 2. X 540. Osmic- 



acidanilin -violet preparation. 

 Fig. 9. Four ztospoies of J. Americana fixed at the moment of escape; from two sporangia, a and b. X 540. 



Osmic acid-anilin-violet preparation. 

 Fig. 10. Four tpoiangia of A. Amiricatia successively developed by cymose branching, in the order of the figures 1 



to 4 ; the empty spore-membranes still adhering to two. X 300. 

 Fig. 11. The tip of a sporangium of Aphonimycis sp., with the head of spore-membranes, most of which have been 



vacated ly the spores ; showing a living spoie, z, in its second form, its cilia not clearly visible, and a similar 



spore, 2', killed with iodine to show its cilia. 

 Or-i, a series of stages in the development of a spore which germinated in situ, withoutthe second swarming : a, at 

 10 A.M. ; b, at 10.C9 ; c, at 10.14 ; d. at 10.19 ; e, at 10.29 ;/, at 10.40 ; g, at 11 ; h, at 11 45 ; i, at 13 M. X 540. 

 Fig. 12. Two encysted z( ospores of ^. apiculata. x 800. Corrosive-sublimate-Hsematoxylin preparation. 

 Fig. 13. Beginning of the germination of a zoospore of A. racemosa, after one division of the nucleus. X 940. 



Picricacid-Hsematoxylin preparation. 

 Fig. 14. Renewal ol tpoiangia oi SapioUgnia sp. by growth of new ones into the empty membranes of old ones. 



X 200. 

 Fig. 15. Empty, "nested," membranes of successive sporangia of Saprolegnia sp., the order of their development 



shown,. 1 — 6. X 200. 

 Fig. 16. A part of a sporangium of Dictyvchus sp. ; showing several stages in the escape of the zoospores, and a 



mature zoospore, z. X 540. 

 Fig. 17. Blanching of hypha3 below empty sporangia in Aph. scaber. X 540. 



