GERMINATION AND EMBRYOGENY OF GNETUM GNEMON. 293 



there is, however, in this case, a special adaptation for transfer 

 of the store material, the feeder being formed by which the 

 seedlino- is connected with the endosperm. In this case the 

 organ is composed chiefly of parenchyma. 



Gnetum has the largest seed of the group. As before, the 

 cotyledons soon escape from the seed, and a feeder is formed ; 

 not only is this larger than that of Welwitschia, but there 

 is also found in it a peculiar arrangement of vascular 

 bundles, the function of which is obviously to facilitate the 

 supply of the nutritive materials of- the endosperm to the 

 stem and root of the seedling. 



The feeder of Gnetum is, like that of Welwitschia, formed 

 by lateral extension of tissues of the hypocotyledonary stem ; 

 the morphological value of the organ in both cases is that 

 of an emergence. The feeder of Gnetum may be compared 

 structurally with the complicated emergences on the exte- 

 rior of the fruit of Datura and ^Esculus, since in both cases 

 vascular bundles enter them. 



It has already been shown (' Quart. Journ. Micr. Sci.,' 

 Jan., 1881) that the outgrowth of the tissues of the hypo- 

 cotyledonary axis (feeder) of Welwitschia is equivalent to 

 the foot described by Pfeffer in Selaginella, and it was there 

 pointed out that those organs in these two genera are alike 

 in their physiological functions, as well as in their struc- 

 ture and position ; they differ slightly, however, in their 

 time of appearance. A similar comparison may be drawn 

 between the feeder of Welwitschia and the foot of Isoetes.^ 



It cannot be doubted that the outgrowth on the hypocoty- 

 ledonary axis of Gnetum is equally the equivalent of these 

 structures, though it owes its origin to an activity of growth 

 of more deeply-seated tissues. 



Looking at these several structures, when fully developed, 

 from the purely histological point of view, we see that in 

 the cases above cited the outgrowths are formed of tissues 

 similar to those of the rest of the hypocotyledonary axis, 

 and that they owe their origin to an increase of bulk, 

 accompanied by cell division ; but they have no special vas- 

 cular system of their own. 



Viewing the foot of the Fern in a similar manner we are 

 led to a similar conclusion. If, in the case of the Fern, we 



1 Kienitz-Gerloff ('Bot. Zeit.,' ISSl, p. 787) describes the origin of the 

 cotyledon, root and foot in Isoetes from octants of the oosphere. Prom 

 his account it appears that the foot is on the same side of the axis as the 

 cotyledon; and in this his description coincides wilii the figures of 

 Hofmeister. He then goes on to say that the orientation of these organs 

 is exactly the same (genau dieselbe) as in the Filicines. In the Filicinese, 

 however, the foot is on the opposite side of the axis to the cotyedon. 



