G20 MR. S. LE M. MOOTlE's STUDIES 



nodule-bearing filament. The third cell has just divided, and the 

 nodule-bearing filament has not yet put in an appearance. The lower- 

 most cell has already divided. Chloriodide-of-zine preparation. X GOO. 

 Fig. 43. Wide cells of the same in an early condition, some distance below the 

 growing-point ; at least three nodule-bearing threads are visible 

 through the incomplete wali of partition. X 600. 



44. A ring at the stage of fig. 43, showing the small slimy membrane and 



three apparently open secondary rings. X 450. 



45. Polysiphonia nigrescens. A ring interposed between the axial cell and 



a cortical siphon, showing division of the protoplasm in passing it. 

 X 600. 



46. An axial-siphonal ring, from above. X 600. 



47. Longitudinal section through the junction of two axial cells of the 



same, showing a large primary ring with secondary rings. X 300. 



48. The same in transverse section, showing a large part of the bottom of 



a cell covered in with membrane, upon the circumference of which 

 secondary rings are here and there to be seen. X 450. (The wall 

 of this has been drawn rather too thick, and at the expense of the 

 membrane.) 



49. Connection between the axial cell and a small cell in the neighbourhood 



of the siphons. There were twenty siphon cells in this section. 

 X 450. 



50. Ring between two siphons of the same, showing division of the proto- 



plasm before reaching it. X 450. 



51. Protoplast from an axial cell of Polysiphonia fastigiata, showing a 



ring wth perforated membrane. From a teased preparation pre- 

 viously boiled in caustic potash, and subsequently stained with chlor- 

 iodide of zinc. X 450. 



52. Half-profile view of a ring of Halurus equisetifolius, obtained in longi- 



tudinal section of the corticated part of a branch. X 450. 



53. Membrane of a small ring between the ultimate and penultimate cell 



of a branch of the same. The preparation was boiled in caustic 

 potash and stained with picric blue. X 600. 



54. Ballia callitricka. View of the junction of two axial cells of a branch 



before cortication has advanced to them. X 450. 



55. The same, showing fine threads of protoplasm attached to the circum- 



ference of a stopper, the intercellular pit filled with membrane &c. 

 Drawn with Hartnack's No. 8 objective, ocular No. 4, but not to scale. 



56. Two stoppers with threads of protoplasm piercing the pit-closing 



membrane. (Chloriodide-of-zinc preparation.) X 450. 



57. Longitudinal section of a corticated part of a branch of the same, 



showing a greatly enlarged stopper ; from it the protoplasm extended 

 as a wide band to the stopper in the floor of the cell. X 450. 



58. Apex of a slender branch. The stoppers are represented by a piece of 



highly refractive protoplasm at either end of the unclosed protoplasm- 

 filled pit. x 000. 

 50. Part of a siphon-cell of Polysiphonia nigrescens, showing reticulate 

 protoplasm on its wall. X <6<>0. 



