EXPLANATION OF THE PLATES. 257 



PLATE X. 



Fig. la. A frond of Sirosiphon pulvinatus, Breb., var. parvus, from a specimen collected by 

 Dr. J. G. Hunt, near Philadelphia. The ground color of this figure is too yellow. 

 Fig. 16. A fragment of the same, magnified 460 diameters. 



Fig. 2. A row of cells of Pleurococcus seriatua, Wood, magnified 460 diameters. 



Fig. 3 a. A portion of the old external part of a mass of Palmdla Jessenii, Wood, magnified 750 

 diameters. 



Fig. 3 b. A fragment from the .interior of such a mass of the same Jiraplification. 



Fig. 3 c. A portion of the soft jelly of a young actively growing mass, magnified t50 diameters. 



Fig. 4. A frond of Dictyosphserium pulchellum, Wood, magnified 460 diameters. I at first 

 referred this plant to the genus BoTaYOOOCOUS, and distributed some specimens under that generic title, 

 and so marked my original drawing. 



Fig. 5. A slice of a youngish frond of Palmella dura, Wood, magnified 460 diameters. 

 Fig. 5 6. A fragment from an old frond, showing the spores in varions, stnges of growth. The 

 color of the large spores is not nearly dark enough, it should be much more brownish. 



PLATE XI. 



Fig. 1. Different forms of Scenesdesmus polymorphus. Wood, magnified 450 diameters. 



Fig. 2. Scenedesmus quadricauda, Breb., magnified 150 diameters. 



Fig. 3. Scenedesmus rotundatus. Wood, magnified 150 diameters. 



Fig. -4. Ordinary vegetative cells of Palmoglcea clepsydra. Wood, in different stages or con- 

 ditions of life-histofy, magnified 750 diameters. Those cells which have the endochrome mnch 

 broken up are believed to be preparing for conjugation. 



Fig. 4 a. A pair of cells uniting in conjugation. 



Fig. 4 6. Cells which have united so that the young spore is very apparent with the empty semi- 

 cells of the parents attached to it. 



Fig. 4 c. A more advanced spore and empty semi-cells. 



Figs. 4 d and 4 e. Matured or nearly matured spores, as seen with different focussing ; in the 

 first the upper surface of the spore is especially brought out. All these figures, except 4 6, are 

 magnified 750 diameters. 



Figs. 5 and 5 a. Different forms of Glosterium acerosum (Schr.), magnified 250 diameters. 



Fig. 5 6. Empty conjugating cells with nearly matured spore. 



Fig. 6. Outline of Glosterium areolatum, Wood, magnified 160 diameters. 



Fig. 6 a. End of a dead, empty frond, enlarged 1375 diameters. 



Fig. 7. Outline of Glosterium Venus, Ktz., magni^ed 450 diameters. 



(These last three species are incorrectly labelled on the plate, Gosmarium.) 



PLATE XTI. 



Fig. 1. Glosterium lineatum, Ehrb. (Incorrectly labelled on the plate Gosmarium.) Magni- 

 fied 160 diameters. 



Fig. 2. Glosterium Ehrenhergii, Menegh., magnified 160 diameters. 

 Fig. 3. Glosterium rostratum, Ehrb., magnified 260 diameters. 

 Fig. 4. Glosterium Dianse, Ehrb., magnified 260 diameters. 



Fig. 5. Glosterium parvulum, Na)g., magnified 450 diameters. 

 33 October, 1872. 



