, % 
A pogamy in Ferns. 1 7 1 
1. The prothallia are both soral and (very rarely) apical, and the 
expanded type greatly predominates over the bulbous form. 
2. Sexual organs are very freely produced, and the antherozoids are 
very active, and are chemiotactically attracted by the archegonial contents, 
some of them even reaching the venter. 
3. No true fertilization occurs. 
4. No migration of prothallial nuclei were observed. 
5. The egg develops apogamously, and in its earlier ontogenetic stages 
follows (though not exactly) the ordinary Fern type. 
6. The cells of the sporophyte and of the prothallium are larger than 
those of the type Fern, and smaller than those of the var. clarissima , Jones. 
3. Athyrium Filix-foemina var. unco-glomeratum , Stansfield. 1 
We owe material of this plant to the kindness of Mr. Druery, who in 
1904 gave us part of a frond, which on being pegged down produced 
aposporous prothallia, both from the sori and apices of the pinnae. Two 
sporophytes were raised, one of which ‘ reverted ’ to the ordinary type of 
A. Filix-foemina , whilst the other one kept true to the varietal form. It 
produced the aborting sori during the summer of 1906, and from these 
fronds we have obtained enough material to work out the general outlines 
of development, though not in full detail. We propose to investigate this 
form further, and also the future behaviour of the descendants of the 
reverted plant. 
The prothallia spring, as has been said, from the abortive sporangia 
and also from the apices and margins of the frond, which are notably 
pellucid in texture. The sporangia are not numerous, and they are 
remarkably elongated ; the prothallia commonly springing from the 
apical (or terminal) cell. Like those of var. clarissima , Jones, the pro- 
thallia are of the expanded and bulbous types, though the latter are not 
so markedly different from the former as in that variety. They resemble 
rather a prothallium that has been almost reduced to a cushion, but they 
often bear filamentous outgrowths. The expanded prothallia commonly 
possess fimbriated edges, and this peculiarity (also shared with clarissima , 
Jones) is to be associated with numerous adventitious marginal growing- 
points of limited duration. Such new growing-points may even arise from 
the marginal cells of the sinus close to the principal apical cell. Archegonia 
and antheridia are both produced. We have not succeeded in raising 
enough sporophytes to clear up the embryogeny. But it is certain that 
the embryo arises endogenously and in connexion with an archegonium, 
and that it possesses a somewhat rudimentary foot. These facts indicate 
1 Cf. Stansfield, F. W., On the Production of Apospory by Environment in Athyrium Filix- 
foemina var. unco-glomeratitm. Journ. of the Lin. Soc., vol. xxxiv. 
O 
