1 1 8 Walker. — On Abnormal Cell-fusion in the 
nucleolus in the higher plants, embedded in a violet staining substance, the 
chromatin. The peripheral region of the nucleus is occupied by an exceed- 
ingly delicate reticulum, and this is connected with the centrally placed 
nucleolus by fine threads. At the points of insertion of these threads the 
chromatin of the nucleolus is drawn out into minute prominences. Fig. i 
shows a surface view of the reticulum with droplets of chromatin at the 
intersections of the threads and the nucleolus lying beneath. In Fig. 2 are 
seen the radiating threads (the ‘ suspending threads ’ of Wager). J. and W. 
van Leeuwen-Reijnvaan in their account of the spermatogenic cells of 
P olytrichum do not describe the region of the nucleus between the nucleolus 
and the nuclear membrane, and in their figures leave it empty. Woodburn 
(23) describes a nucleus similar to that of Polytrichum in the young sperma- 
togenic cells of Porella but makes no mention of suspending threads. 
In M archantia, according to Woodburn (23), the nucleus in the resting con- 
dition ‘ shows an evident linin network containing relatively large lumps of 
chromatin in a clear nuclear sap without any nucleolus \ It seems probable 
that the single large nucleolus described in Porella by Woodburn, in Pellia 
and Mnium by Wilson, and in Polytrichum , simply represents a closer 
aggregation of the chromatin material than occurs in Marchantia according 
to Woodburn (23), and in Fegatella according to Bolleter (5), where several 
large lumps are found. In Polytrichum , as will be shown later, the nucleus 
shortly after division exhibits scattered lumps of chromatin, but this phase 
is soon passed over and the lumps collect to form a single central body. 
Wilsons account of the nuclear reticulum in the archesporial ( 21 ) and 
spermatogenic cells (22) of Mnium hornum differs somewhat from the fore- 
going. He states that ‘ the nuclear network is fine and closely resembles 
the cytoplasm in structure, no chromatin being present in it during the 
resting condition ’. Wilson’s drawing of a spermatogenic cell (Fig. 1 in his 
paper) fails, however, to show the nuclear reticulum which he describes. 
This drawing agrees with certain appearances sometimes seen in the resting 
nuclei in young spermatogenic cells of Polytrichum (Fig. 3 ), where the ground 
substance of the nucleus presents a finely granular appearance, suggesting 
the possibility that the network has been masked by a fine granular 
substance, perhaps precipitated by the fixative. A more or less distinct 
reticulum, however, may generally be seen even in young cells of the 
antheridium, and is a constant feature of nuclei of the later cells and of the 
nuclei of the vegetative parts. Wilson further adds that a nucleus of this 
type (Fig. 1 in his paper and resembling Fig. 3 in the present account) can 
be considered characteristic of the Muscineae. With regard to its general 
structure the Bryophyte nucleus as described by Beer (3) in Riccia , by 
Van Hook (18) in Marchantia , by Woodburn (23) in Porella^ and according 
to the present description in Polytrichum , does not appear to differ very 
greatly from that of the higher plants. Both in regard to the large size 
