GERMINATION AND HISTOLOGY OF WELWITSCHIA MIRABILIS. 27 
specially modified organ, devolves either on reduced cotyle- 
dons (e.g. Palme, Graminez, Cycas, Ginkgo), or on 
haustoria, specially developed from the suspensor (Tro- 
peolum).! If we turn, however, to the vascular Cryp- 
togams, we shall be able to trace a parallelism. In Sela- 
ginella we have a case which is very similar to that of 
Welwitschia. There the hypo-cotyledonary stem grows out 
laterally to form the so-called foot of Pfeffer.” 
Whatever may be the embryo-genetic relation of this 
structure to the other parts of the embryo, as compared with 
the case of the Filicinez,® still the fact remains, that in 
Selaginella the so-called foot is produced by the lateral 
extension of the tissues of the hypo-cotyledonary stem, accom- 
panied by cell divisions in the cortical tissue. Further, on 
examining the figures of Pfeffer, it will be seen that the 
series of cells, though slightly complicated by tangential 
divisions, may, as in Welwitschia, be traced curving out- 
wards into the lateral organ; and since, as in Welwitschia, 
there is no fibro-vascular bundle peculiar to the organ, we 
see that the correspondence from the histological side is 
complete. The correspondence between the two organs is 
also perfect from the physiological side. The only difference 
then lies in the time of appearance of the two organs, and 
this only a natural result of the difference in position of the 
latent period in the cycle of life of the two plants. While, 
then, the feeder of Welwitschia,'and the so-called foot of 
Selaginella, must be considered as the analogues of the foot of 
the Filicinez, when regarded from the physiological point of 
view, still (holding as I do that the term foot implies an 
embryogenetic relation to the other parts of the embryo, and 
since the feeder does not bear that relation to them) I have 
avoided using the term foot, and supplied its place with a 
name, which implies no preconceived morphological idea. 
Besides the so-called foot of Selaginella, there is, in the 
higher plants also, a parallel case to that of Welwitschia. 
But the correspondence is here only morphological. In the 
1 Dickson, “On Embryogeny of Tropeolum, &c.,” ‘Trans. Roy. Soc.’ 
Edin., 1875. It must be noticed that here the nutritive substances are 
derived from the carpel. 
2 *Bot. Abb.’ Herausgegeben v. Hanstein. Heft i. 
3 Cf. Vines, ‘Quart. Journ. Mier. Sci.,’ vol. xviii, New Series, p. 57. 
The question of homology of the suspensor, there discussed, seems to de- 
pend upon the definition of the term foot. If it implies a structure de- 
signed to meet a certain physiological need, the feeder would fall under 
the definition; if it be used to imply a structure whose embryo-genetic 
relations are constant, I do not see how the organ in Selaginella or in 
Welwitschia can be included. 
