709 



themselves, as to leave no doubt of their relation. Compare, for in- 

 stance, Lycopodium Phlegmaria and Cunninghamia siamensis. Some 

 cycads have the gyrate vernation of the leaves of true ferns, along 

 with the inflorescence of conifers ; and their mode of forming their 

 trunk, although essentially the same as that of exogens, yet resembles 

 the growth of acrogens in lengthening by a terminal bud only. 



While, however, the class of gymnogens is thus distinctly mai'ked by 

 the most important physiological peculiarities, it approaches the high- 

 est forms of vegetation by that portion of it which bears the name of 

 joint-firs, plants with all the structure of their class, but with the 

 manner of growth of chloranths and beef-woods," — L. V. K. 221.* 



The Rhizogens are a peculiar tribe, and have become intimately 

 known to botanists through the descriptions of Robert Brown and 

 the inimitable figures of Bauer, published in the " Transactions of the 

 Linnean Society of London." It will be sufl&cient to mention the re- 

 markable genus Rafilesia as the type of this class, in order to place 

 the class itself fully before the mind of a botanist. Mr. Lindley cha- 

 racterises therhizogens as flowering, sexual plants, whose fructification 

 springs from a thallus. Notwithstanding the labours of Robert Brown 

 we are still in ignorance of many essential characters of these plants : 

 we see nothing more than a huge, fleshy flower, sessile on the root or 

 rhizoma of some other vegetable ; there is no stem, leaf, or root ; the 

 vast expanded flower is all that we can see. Many botanists have 

 considered it phaenogamous, others cryptogamous. The substance on 

 which it grows must receive farther investigation, the nature of its con- 

 nexion with the flower is a point of the greatest interest : — Mr. 

 Lindley's idea of its afiinities is conveyed in this passage. " At 

 this point of the Vegetable Kingdom we find a most curious assem- 

 blage, which, with many of the peculiarities of endogens, seem to be 

 an intermediate form of organization between them and thallogens. 



* " Among exogens there are, however, two totally different modes in which the in- 

 fluence of the pollen is communicated to the seed. The larger part of this great class 

 consists of plants provided with the apparatus called style and stigma, through which 

 pollen-tubes are introduced into the ovary during the act of fertilization. But others 

 are so constructed that the pollen falls immediately upon the ovules, without the in- 

 troduction of any intermediate apparatus ; a peculiarity analogous to what occurs 

 among reptiles in the Animal Kingdom: and, as was to have been anticipated, the 

 plants in which this singular habit occurs prove, upon being collected together, to 

 form a group having no direct affinity with those among which they had been previ- 

 ously associated. Hence exogens have been broken up into, — 1. Exogens proper, or 

 those having an ovary, style, and stigma; and 2. Gymnogens, which have neither.''^ 

 Lindley, Veg. Kingd. 4. 



Vol. II. 4 u 



