JOURNAL OF MICROSCOPICAL SCIENCE. 



DESCRIPTION OF PLATE III., 



Illustrating Pringsheim's paper on the Impregnatiou and 

 Germination of Algae. 



p. Figs. 1 to 20, Vaucheria sessUis, multiplied 250 diameters. 



1 to 4. — Stages of development of the sexual organs before impregnation. 

 5. — The sexual organs during impregnation. 



6 to 8. — The way in which the female organ (the so-termed " spore") 

 opens, the " cutaneous layer" bursts through, and a portion is 

 constricted off. 

 9. — Approach of the spermatozoids to the female organ before the forma- 

 tion of the membrane of the embryo-cell (the true spore). 



10, — The point of the female sexual organ after the iormation of the 

 membrane of the true spore. 



11, 12. — Later condition of the spore, after impregnation. 



13 to 16. — Later condition of the male and female organs after impregna- 

 tion. They show the subsequent slow detachment of the mem- 

 brane of the male organ (the antheridium formed out of the 

 summit of the " hornlet"), and the gradual decoloration of the 

 contents of the spore, lying in the female sexual organ (the S2W- 

 rangiuvi). 



17. — Colourless spore after it has become detached from the parent tube. 



18. — A spore detached from the tube, which after long rest (three months) 

 has again become green ; an indication of its awakening develop- 

 ment. 



19, 20. — Germination of the viridescent spores. 



Figs. 21 to 24, FucHs vesiculosus, multiplied 200 diameters. 



21. — Large spore {sporangium), whose contents the eight still connected 

 " division spores" have escajied. 



22. — " Division s^wres," isolated before impregnation ; the clear central 

 spot shows the true cell-cavity filled merely with fluid, 



23. — Division spore after impregnation. The spermatozoids may be seen 

 within the membrane. 



24. — Earlier state of germination of an impregnated " division spore." 

 Fig. 25, Sphacelaria tribuloides, multiplied 300 diameters. 



25. — Propagative gemmule, whose terminal cell transformed into a 

 S'phacela contains an antheridium partly emptied and partly filled 

 with spermatozoids. 

 Figs. 26, 27, CEdogonium tumidulum, multiplied 350 diameters. 



26, 27. — Sporangium during (fig. 26) and after (fig. 27) the formation 

 of the micropyle for the spermatozoids. 



Figs. 28 to 34, Bulhochcete, multiplied 250 diameters. 



28. — Sporangium of Bulhochcrte setigera ; the passage into the interior of 

 the sporangium is already formed by a transverse fissure of the 

 membrane. A microgojiidium has germinated upon the spo- 

 rangium, and discharged its contents. 



29. — A similar condition in a sp)orangiiim of B. crassia (n. sp.) 



30, 31. — Sporangia of B. intermedia, ruptured in consequence of the 

 incipient develoimient of the spore. The spore, covered only by the 

 innermost layer of the cell-wall, has escaped from the sporangium. 



32. — The liberated spore is somewhat elongated, and 



33. — Its contents divided into four portions. 



34. — The division is completed ; the four reddish green zoospores, produced 

 from the contents of the quiescent spore, are already fully formed. 



