The Cytology of the Cladophoraceae. 
BY 
NELLIE CARTER, D.Sc. 
With Plate XXVII and two figures in the Text. 
.THOUGH the nature of the cell-wall and branching of Cladophora 
1Y and Rhizoclonium has recently been investigated by Brand (1895, 
1898, 1899, 1901, 1902, 1904, 1906, 1908, 1909), and a systematic 
account of the genus Rhizoclonium has been given by Stockmeyer (1890), 
no exact information has been obtained concerning the cytology of the 
Cladophoraceae, and with the exception of the rather scanty observations 
made by Borzi (1883), Schmitz (1879,- 1882), Gay (1891), and others, and 
the more recent work of Wille (1901) on Rhizoclonium , very little is known 
of the internal structure of the frequently very large coenocytes which form 
the thallus in species of this family. 
In Kiitzing’s original descriptions of the three genera Chaetomorpha , 
Rhizoclonium , and Cladophora , no information at all is given concerning 
the internal structure of Chaetomorpha , whilst for Cladophora he gives the 
description, ‘ Substantia gonimica primum cryptogonimica, effusa, demum 
granulosa et amylacea, saepissime in lineas laxe spirales ordinata ', and 
for Rhizoclonium, ‘ substantia gonimica viridis subtiliter granulosa et 
aequaliter diffusa \ 
Schmitz (1879) noticed the variability of the chloroplasts in Cladophora 
glomerata and CL fracta , and remarks that in these two species and also 
in Chaetomorpha the cell-cavity is usually traversed by an internal network 
of protoplasm, and that on some occasions chloroplasts are also contained 
in these internal protoplasmic strands. In a later work (1882) Schmitz 
figures the chloroplast of Cladophora arcta as a much perforated parietal 
sheath, and says that in other species of the genus the chloroplast is much 
more perforated and lobed, and from it arise numerous band-like outgrowths 
which penetrate the interior of the cell and fill it with a coarse green net- 
work. He also observed that in many members of the Siphonocladiaceae, 
including species of Cladophora , the single parietal cylinder seems to have 
been divided to form numerous small plates of varying size and form. 
Strassburger (1880) also found that the chloroplast in Cladophora 
consisted of a more or less netlike parietal sheath or else plates of irregular 
I Annals of Botany, Vol. XXXIII. No. CXXXII. October, 1919.] 
