648 Lewis. — The Life History of Griffithsia Bornetiana . 
though here, too, the counting is made difficult by the presence of a darkly 
staining substance between the chromosomes (Figs. 29, 30, 31). 
Mitoses of the type described above have been observed in vegetative 
cells of various ages, in the hair-cells of the procarp and cystocarp, in the 
primary tetrasporic cells, in the stalk-cells of the tetrasporangia, in the 
involucral cells of the tetraspore-sorus, in the sporelings from tetraspores, 
and in the sporelings from carpospores. 
No undoubted cases of amitosis have been observed. An appearance 
suggesting amitosis has been noted in the stalk-cells of the tetrasporangium 
and in the cells of the sporogenous lobes, and may possibly occur in the 
vegetative cells ; but the small size of the nuclei renders exact observation 
on this point very difficult. It may be said with certainty, however, that 
the usual mode of nuclear division is by mitosis. 
It may be well to compare at this point the behaviour of the nuclei in 
division with those of Polysiphonia (Yamanouchi) and Nemalion (Wolfe), 
the two other red algae which have been carefully studied from the cyto- 
logical standpoint. 
Resting nucleus. 
Origin of 
Chromosomes. 
No. of 
chroms. 
Poles of 
spindle . 
Nucleolus. 
Nemalion 
Chromatin in 
central nucleolus 
Chromatin 
passes to 
periphery 
8(16) 
centrosomes 
karyosome 
Polysiphonia 
Chromatin in 
peripheral network 
Derived from 
chromatin 
network 
2° (40) 
centrosphere 
like bodies 
plasmosome 
Griffithsia 
Chromatin in 
central nucleolus 
Chromatin 
passes into 
nuclear cavity 
7 (H) 
kinoplasmic 
caps 
karyosome 
The chromatophores are numerous, small, oval or round, flattened 
bodies of rosy pink colour lying in the granular cytoplasm next the cell-wall. 
They vary considerably in size ; on an average, each is about 3-5 \i long, 
2*5 M broad, and i*2/x thick. Usually the outline of the chromatophore is 
smooth (Fig. 33), but occasionally it is toothed, as is true in other species of 
Griffithsia. In the younger cells the chromatophores are crowded together 
without definite arrangement. In the older cells they often occur in curved 
rows, which are arranged in the form of an irregular network (Fig. 32), as 
was described for other species of Griffithsia by Berthold (7), and for many 
genera of the Siphonocladiaceae by Schmitz (67). 
The number of chromatophores in a cell is very large. In an older 
cell of average size, about 400,000 were estimated to be present. 
The chromatophores in the protoplasmic pads lying on the cross-walls 
are much fewer in number and smaller than in other portions of the 
cytoplasm. 
