208 THE BOTANICAL MAGAZINE tVoi. xxxv. No. 4t9. 



often an obstacle to the work of preparation ; for, even in the fixed 

 material it often shrinks or swells up according to the reagents 

 applied for the preparation. 



A larger part of the cell is occupied by a stellate chromato- 

 phore ; the centre of the latter lies in the central part of the cell and 

 gives off radiating arms toward the wall, where they become 

 flattened against the inner surface of the cell wall. It is brightly 

 stained with acid fuchin, light green and haematoxylin. A single 

 spherical pyrenoid of Porphyra or Baagia has often been taken as 

 the nucleus by many investigators, on account of its similarity in 

 position, size and appearance. In the ground substance of the peri- 

 pheral portion of pyrenoid, minute fusiform corpuscules are found, 

 which are mostly arranged beneath the surface parallel with one 

 another as shown in Fig. I. They are stained with haematoxylin, 

 but neither with acid fuchsin nor light green ; iodine reaction for 

 starch is negative. Some detailed accounts of these corpuscles will be 

 given in another day. The ground substance of the pyrenoid is 

 homogeneous and is brightly stained with acid fuchsin but less so 

 with light green. 



The nucleus is very minute, generally spherical in shape, situated 

 in the excentric portion of cell and mostly lies near a radiating arm 

 of chroraatophore. It measures usually about 1.5-2/i in diameter. 

 In the living state nucleus is quite difficult to detect, but when 

 treated with an aqueous solution of picrie acid, it becomes clearly 

 differentiated and easily visible as a refractive globule. In a section 

 obtained from a material well fixed and stained with haematoxylin, 

 it appears as a soUd black sphere destitute of any other minute 

 structure, except that a hyaline globule is occasionally present with- 

 in it, as illustrated in Fig. I. c. Possibly the chromatic substance 

 may be homogeneously distributed in the ground substance of nuc- 

 leus, since the nucleus shows no structural differentiation. In external 

 appearance it has a close resemblance with the karyosome of higher 

 plant, or it looks like a central chromatic portion deprived of the 

 external hyaline space in the nuclens of a certain species of Phycomy- 

 cetes. 



The process of the nuclear division is very peculiar ; it assumes 

 a type intermediate between mitosis and amitosis. An achromatic 

 space, mostly fusiform in shape, makes its appearance in the nucleus 

 which is in the preparation for nuclear division, and as it develops, 

 the nucleus becomes elongated and assumes a spindle shape. The 



