GERMINATION AND EMBRYOGENY OF GNETUM GNEMON. 297 



arise only when and where they are required for the first 

 processes of development and nutrition of the young 

 emhryo. 



If now the term " foot" be applied to such outgrowths of 

 tissue as appear on the hypocotyledonary axis (such as are 

 found in the embryo of the vascular Cryptogams), and if the 

 term be understood as not implying that the swelling holds 

 any definite orientation relatively to the other parts of the 

 embryo, or is connected essentially with any of the first 

 divisions of the fertilised oosphere, the term " foot" might 

 equally well be extended, so as to include all the cases of 

 lateral outgrowth above enumerated, while it has this further 

 advantage over the term " feeder," previously adopted for the 

 lateral outgrowth in Welwitschia, that whereas in the ma- 

 jority of cases (vascular Cryptogams and Gnetacese) the 

 function of the organ is chiefly one of nutrition ; in the 

 Angiosperms only a mechanical function has been ascribed 

 to it, and the term ^^foot" does not imply any special 

 function. 



Returning now to the seedling of Gnetum Qnemon : 



The arrangement of parts at the apex of the seedling is 

 very similar in the three genera of the Gnetaceee. There 

 are found at a certain stage in each a pair of opposite coty- 

 ledons, a pair of plumular leaves decussating with these, a 

 central apical cone, and a lateral bud in the axil of each of 

 the cotyledons. In fact, in number and arrangement of 

 parts the seedlings of the three genera are identical. From 

 this point starts that divergence of character which makes 

 the Gnetacese one of the most remarkable groups in the 

 vegetable kingdom. In IVehoitschia the further develop- 

 ment of appendicular organs is arrested (with the exception 

 of the adventitious fertile branches), while those already 

 formed increase in size, or are thrown off (cotyledons). The 

 internode between the cotyledons and plumular leaves 

 remains in this case short. In Ephedra the above organs 

 only attain a very limited size. At the apex are formed 

 fresh decussating leaves with buds in their axils and elon- 

 gated internodes. All the leaves with exception of the long 

 linear cotyledons remain of a small size. 



In Gnetum the development of fresh leaves proceeds as in 

 Ephedra, but these have an expanded lamina and reticulate 

 venation. Thus, from seedlings which are very closely 

 similar are derived plants of most different habit. 



The vascular system of Gnetum Gnemon differs from that 

 of the other two genera, and the difference seems to depend 

 to a great extent upon the fact that an uneven number of 



