Apogamy in Ferns, 167 
In no single instance did such vegetative reproduction of the sporophyte 
occur in our cultures. 
No cases of migration of nuclei in the prothallial tissue of this variety 
have been seen. 
The chromosomes of various parts of the embryo, taken from the 
young stem-leaf and root, have been counted, and the average numbers (90) 
very closely approximate to those obtained as the result of a study of the 
prothallial cells. 
Cell Sizes. A remarkable difference exists between the cells of this 
plant and that of the type species (see below, p. 185). The cells and nuclei 
of the variety are very obviously of a larger size, and the same feature is 
also shared by the antherozoids (cf. Figs. 16 and 34). 
Summarizing the results obtained from a study of this Fern, we may 
present them as follows : — 
1. There are two types of prothallium, the expanded and the bulbous. 
The latter almost alone (in our cultures) bore sporophytes. 
2. No change in the number of the chromosomes marks the transition 
from one stage in the life-history to another. 
3. There is no migration of nuclei from one prothallial cell to 
another. 
4. The nucleoli of the gametophyte are peculiar, and different from 
those of the prothallial nuclei of the type form. 
5. The archegonia, although they are never fertilized, exert a chemio- 
tactic influence upon the antherozoids which are very actively motile. 
6. The embryo arises as a bud upon the gametophyte. 
7. The cells, nuclei, and antherozoids of the variety each have a proper 
size which differs from that of the type Fern. 
2. A thyrium Filix-foemina var. clarissima , Bolton. 
This Fern was discovered in Lancashire by Mr. T. Bolton, who found 
it growing wild in 1892. It very closely resembles the preceding variety 
except that the ultimate branches of the leaves are somewhat spiral in 
character. The aposporous nature of the plant was established by 
Mr. Druery, who discovered that the prothallia were not only associated 
with the sori of (invariably) sterile sporangia, but that they might also 
occasionally arise directly from the apices of the pinnae. 
Mr. Druery has twice given 11s fronds of this Fern, and they proved remark- 
ably prolific, the prothallia appearing in crowds on pegging the frond down 
on damp soil. Unlike the preceding variety ( clarissima , Jones), the pro- 
thallia produced by this plant are fertile to an extraordinary degree, and 
there is no difficulty in getting a large supply of embryos. We have 
grown some of the young sporophytes produced from the first lot of 
