IN VEGETABLE BIOLOGY. G19 



of their passage through it (glycerine preparation), b. A ring from 

 the front, showing threads passing through it. Such a view as the 

 last can only be gained by a great deal of focusing (chloriodide-of-zinc 

 preparation), x 600. 

 Fig. 27. The same, Apparent direct continuity of the small outer cells. The 

 parietal protoplasm lies as a dense highly refractive layer upon almost 

 the whole of the wall, x 600. 



28. Connection between the short cells, isolating and the long cells lying in 



the chambers of Chylocladia articulata. Not drawn to scale. 



29. Rings between the long cells of the same, from above. From sections 



dyed with Judson's Oxford blue. X 600. 



30. Continuity through the rings between the chamber-isolating cells of the 



same. From a section treated similarly to the last. X 600. 



31. Callithamnion sp. (a) A tip of a branch showing divided nuclei, 



achromatin fibres, and a commencing cell-plate. X 600. (b) A 

 smaller tip than the above, the cell- wall fully formed, the protoplasm 

 in continuity by means of a fine thread, at either end of which is 

 placed a highly refractive piece of protoplasm. Chloriodide-of-zinc 

 preparation. X 450. 



32. Cell-junctions of the same, further developed. The rupture of the ring 



(fig. b) has brought into view several fine threads issuing from its 

 membrane. Fig. a X 450, fig. b X 600. 



33. Ptilota sericea. A small ring from a branch shortly before cortication ; 



perforated membrane already developed. Chloriodide-of-zinc prepa- 

 ration, x 600. 



34. Connection between axial cells near the bottom of the frond of the 



same : a, in longitudinal, b, in transverse section. X 450. 



35. Delesseria alata. View of the membrane-closed bottom of a large cell, 



from above, showing a large primary ring and circumferential 

 secondary rings. X 450. 



Plate XXI. 

 Fig. 36. The same. Cell-junction in longitudinal section. X 450. In this 

 and the last : p, primary ring ; s, secondary ring ; m, membrane. 



37. Division of protoplasm in passing the rings of the same. The dark line 



on either side of the ring in fig. a is the primary ring. X 450. 



38. The same. Rings, from above. X 600. 



39. A small, apparently simple ring, between two of the large cells of the 



same. X 450. 



40. A membrane from a ring, showing two small rings near its centre. 



X450. 



41. A primary ring with small secondary rings interposed between two of 



the cells which surround the large cells of Delesseria alata. From a 

 preparation placed for eighteen hours in chloriodide of zinc. X 450. 



42. Row of long cells from which the midrib of Delesseria alata is built up. 



The uppermost came fourth in order behind the scutcheon-shaped 

 cell formed by division of the third demilune cell. The second cell 

 is preparing for division ; it is connected with its fellows by a fine 



