590 
Notes . 
gametophyte from the tissues of the sporophyte, are briefly these. 
In Mosses cut portions of the seta or capsule have been induced 
to give rise to protonemal filaments; in one case this is known to 
have occurred in nature while the capsule was still attached to the 
Moss plant. In a number of Ferns the production of prothalli from 
the sporangia, the placenta, the surface of the leaf or the leaf margin, 
takes place. In Scolopendrium vulgare and Nephrodium Filix-mas 
varieties are known in which the first leaves of the young sporophyte 
exhibit this capability of producing prothalli. The causation of this 
phenomenon is still obscure. In a number of cases sporal arrest has 
been shown with probability to be of importance, notably in the case 
of Onoclea, in which apospory occurred on fertile leaves which had 
been experimentally induced to assume the vegetative form. Further, 
the fact that conditions of life favourable to the gametophyte, such 
as laying the fronds on damp soil, determine the growth of prothalli 
from the tissues of some aposporous Ferns may be mentioned. 
As to the weight to be attached to apospory it must be borne in 
mind that the phenomenon is little more wonderful than the fact 
of the spore, a cell isolated from the sporophyte, producing a pro- 
thallus. Here, as in the case of apogamy, the investigation of the 
cytological details is urgently needed. 
The deviations from the normal life-history, which are classed as 
apogamy, may be considered to possess more importance as suggesting 
the homology of the two generations in the Ferns. Though as yet 
only known in this group of plants, apogamy has been found in more 
than twenty species. In some the young Fern-plant arises on the 
under surface of the prothallus, which in these cases often bears 
few or no sexual organs. But in cases in which apogamy has been 
induced the characters of the two generations may be much more 
intimately blended. Thus tracheides may occur in a prothallus more 
or less modified in external form. This may grow on as a bud, or 
may bear isolated members of the sporophyte, leaves, roots, ramenta, 
or sporangia. The characters of the two generations are here united 
in the same individual in a way that at least suggests a gradual 
transition from gametophyte to sporophyte. 
It is to be hoped that the further study of these deviations from the 
normal development will lead to their causation being made clear. 
This may minimize the importance to be attached to them, especially 
should they be found to depend on a nuclear change. The facts 
