154 REVIEWS. 



returns. But in Welwitschia the two leaves are permanent. 

 AVherefore they are firm and coriaceous, and, increasing by 

 basal growth from year to year, the older parts doubtless 

 become inactive at length, while fresh surface below is an- 

 nually renewed, under the shelter (as Dr. Hooker describes) 

 afforded by the deep grooves which in old plants separate the 

 growth of the hypocotyledonary stock from that of the crown 

 above, and is filled by the tender growing bases of the leaves. 

 Having given a detailed generic character of Welwitschia 

 and a comparative view of the Gnetaceous genera, now three 

 in number, Dr. Hooker proceeds to describe at length the 

 trunk, leaves, inflorescence, flowers, fertilization, embryogeny, 

 and seeds of this curious subject, — comparing it, in the latter 

 respects, with Coniferce and Cycadacece on the one hand, and 

 with Santalum and Loranthus on the other, and closing with 

 a general summary of the results. 



An abstract or analysis of this most important paper is 

 beyond our present reach and space. But we may refer to 

 some of the special points. 



The most obvious peculiarity of Welwitschia is, that " it 

 appears to be the only perennial flowering plant which at no 

 period has other vegetative organs than those proper to the 

 embryo itself, — the main axis being represented by the rad- 

 icle, which becomes a gigantic caulicle, and develops a root 

 from its base and inflorescences from its plumulary end, and 

 the leaves being the two cotyledons in a very highly developed 

 and specialized condition." It is an excellent case, accord- 

 ingly, if any such were still needed for showing the nature 

 of the radicle as stem, or ascending axis (not root), — a view 

 which we supposed observation had long ago demonstrated. 

 Dr. Hooker, in a note, refers to this view as expressed by 

 Adr. de Jussieu in his " Cours Eldmentaire " (which appeared 

 in 1843 and 1844), and in Gray's Introduction to Botany 

 (" Botanical Text Book "), 1858. But the same view is taken 

 in all the earlier editions of the latter work ; even in the first 

 (1842) the radicle is spoken of as the first internode of the 

 stem (p. 28, note) ; and probably the idea will be found dis- 

 tinctly expressed in works of an earlier date. Dr. Hooker, 



