266 Farmer . — On the Embry ogeny of 
development of the prothallium has been followed by Jonk- 
man 1 from the germinating spore, and he observed the 
formation of the sexual organs. Tfie antheridia occur on the 
upper and lower surfaces of the oophyte, though they are 
more freely distributed on the lower side. They arise from 
single superficial cells. Each of these divides into an inner 
and an outer cell. The former by repeated division gives rise 
to the mother-cells of the antherozoids, whilst the latter or 
outer cell divides in planes at right angles to the free surface, 
thus forming the cover-cells, by whose separation the anthe- 
rozoids are eventually liberated from the antheridium. The 
archegonia are confined exclusively to the lower surface of 
the prothallium, and arise from the c cushion ’ region, which is 
exceptionally large in this plant. A superficial cell divides 
periclinally into an outer cell from which the neck of the 
archegonium originates, and an inner cell from which the 
neck- canal and ventral-canal cells are successively cut off, 
leaving the oosphere at the base. The neck-canal-cell grows 
between the cells of the short neck forcing them apart. It 
ultimately divides into two transversely, and the resulting 
cells are often separated by a true wall, as was observed by 
Jonkman, and by Campbell 2 also in the case of Osmunda as 
an occasional occurrence. It is by no means invariable in 
Angiopteris , and in Fig. 2 there is shown a case in which 
the cell-wall, though it had begun to be formed, was not 
completed, and was drawn away with the shrinking of the 
protoplasm, from the lining walls of the neck-canal. The 
ventral-canal-cell, which is very large in this fern, is con- 
verted like the two neck-canal-cells, into mucilage, which on 
the addition of water, bursts open the archegonium. In a 
few cases I observed an apparent deviation from the course 
just described, inasmuch as the inner of the two cells resulting 
from the first division of the archegonial primordium seemed 
to have divided again, before forming the axile row of cells ; 
1 Jonkman, De Geschlachtsgeneratie d. Marattiaceeen. 
2 Campbell, On the Prothallium and Embryo of Osimmda claytoniana and 
Osmunda cinnamomea , Ann. Eot. VI, p. 67. 
