590 MurrilL—The Development of. the Archegonium 
are drawn to the poles as attenuated U’s or V’s (Fig. 27). 
The cell-plate is laid down from the centre outwards. It 
begins in the dispirem stage and keeps pace for some time 
with the growing daughter-nuclei (Figs. 29, 30). The fibres 
thicken at the centre, and the thickened portions fuse together 
at the side. The spindle then broadens out and stretches the 
young cell-plate until it connects with the wall of the mother¬ 
cell (Fig. 31). The original nuclear membrane does not 
entirely disappear until the daughter-nuclei are formed. It 
then splits up into slender fibres and fades away into the 
surrounding cytoplasm. 
The division above described, while it resembles that de¬ 
scribed by Rosen (1895), Hof (1898), Nemec (1899), and 
others for the vegetative cells of various plants, in the extra- 
nuclear origin of the spindle and the details of its construction, 
nevertheless differs very strikingly from that type by reason 
of the fact that the spindle is at first asymmetrical and 
originates in a large fibrous mass beneath the nucleus, which 
appears early, grows to an immense size, and remains for 
some time after the division is completed, being enveloped 
during its existence by numerous fibres radiating from it far 
into the surrounding cytoplasm. 
Various authors (Ikeno, 1898, p. 567; Blackman, 1898; 
Chamberlain, 1899, figs. 1, 2; and others) have described or 
figured the nucleus of the central cell as remaining at the 
cell-apex until division occurs, and it would be interesting 
to know whether more careful study would show such a method 
of spindle-formation as I have discovered in Tsuga in these 
or similar cases of unequal division. 
This collection of cytoplasm is probably due to the need 
of a support for the free lower pole, and the numerous 
radiations from it doubtless add greatly to its stability. The 
origin and growth of the spindle chiefly on the lower side 
of the nucleus seem to indicate that the force controlling 
division is largely centred there. 
