Champia parvula, Harv. from the Carpospore . 345 
parent plant. The boundary of the outside hyaline layer, 
which is simply the thickened outside cell-walls, has been 
indicated in the figures. This layer is perfectly homogeneous, 
showing no striations, which is also true of the other cell- 
walls. The measurements were all made with a Zeiss micro- 
meter eye-piece. 
The third division in the segmentation of the spore seems 
to be in a plane parallel to the substratum, making an 8-celled 
stage out of the 4-celled stage. Fig. 4 gives a side view of the 
8-celled stage. The fourth stage, 16 cells, Fig. 5, is not a 
common one, and probably does not last long, but changes 
quickly into the fifth stage, represented in Fig. 7, which 
consists of 28 cells. 
As shown in Fig. 5, the 16-celled stage develops from the 
8-celled stage, by each of the eight cells being cut by cell- 
walls parallel to the substratum. The cell-walls are probably 
slightly oblique, inclining towards the centre of the embryo. 
Optical sections of later stages seem to indicate this (see 
Fig. 14). In the 16-celled stage the first indication of the 
formation of an organ of attachment appears. This is indi- 
cated by a slight bulging of the four bottom cells of the 
embryo. Fig. 6 represents a top view of the 16-celled stage, 
and shows the four cap-cells with the four cells just below 
them. The fifth stage, Fig. 7, is but slightly different from 
the one preceding it, Fig. 5. Each of the eight cells, arranged 
in a zone between the two groups of four cells at the top 
and bottom, divides by a perpendicular cell-wall. The slight 
processes, which appeared at the bases of the four bottom 
cells, have now been cut off as four separate cells, from which 
are to arise the four organs of attachment. 
With the next stage (Fig. 8) we may consider the segmen- 
tation of the spore complete. In the two figures, 7 and 8, 
numbers have been given to the cells, which seem to be the 
same or to have had the same origin. It will be seen that the 
only change that has occurred has been at the base of the 
embryo. 
The four cells, numbered 5 in Fig. 7, have each given rise 
B b 
