UXOUENS. 



in all thesi ea the deviation 

 the typical character of being dicotyledono 



When the emhryo of an E enniuates, the i . 



at its point, without having to break through tin 

 account Bxogens have been named exorhizal. 



Hence the class <>!' Exogens ha- five important, an. I. in 

 independent characters, l>\ which it- limit- an 



1 . Tin- wood is exogenous. 



2. Tin' veins cit' tin' leaves an- netted. 



'■'■ Tin' fructification is formed upon a quinary or quafc 



1. Tin- emhryo is dicotj ledonous. 



5. Tin- germination i - exorhizal. 



Bxogens have received other appellations in allusion to such • 

 they are commonly called Dicotyledones, ami Bxorhizse is am I 

 common appellation; moreover, they are the Phanerocotyled 



.Hi, the Anthophytse ami Carpophytaa of Oken'6 Bchool, the U 

 -ana of Schultz, the Phylloblastae of Reichenbach ; not t.. mention d 

 still more obscure. 



In consequence of imperfect development, an. I the abortion or mult 

 cation of parts, many deviations occur from the above characters. 

 in Bndogens, jo in these, such anomalies do not cause any real difficulty in 

 distinguishing Bxogens from other plan:-. Suppose the st< m I 

 slightly formed, a- in Mossweeda I Podostemaceae), or the aquatic Hipp . 

 a- not t<> arrive at a state in which the exogenous arrangement 

 hie, we have the dicotyledonous embryo, ami tin- typical number of the 

 floral organs to guide us. Let the leaves appear as scales, 

 Orobanche, ami the like; .-till there is the embryo or again the •' 

 proportions. If the fructification is absolutely ternary as in M< 

 the organisation of the stem, leaves, ami embryo reveals the true i 

 such plants. Or if the embryo is undivided, ..- in Cuscuta, 

 Bame time the veins of the leaves deficient, and all this with an in 

 formation of woody matter, then the number of pan- in th< 

 to prevent our falling into error. It is therefore alwaj 

 that tiie limit- of this great class are m.t exclusively 

 Bingle character, hut bj a combination of five; a part of which ■ 

 occasionally exceptional or undiseovi rable. 



But while the class of Bxogens i- thus distinctly circu 

 found to approach the limits of ether classes at vario 



tenches Gymnogens bj mean- of Beefw 1- Casual 



are represented by Crowfoots, some of the -;•• 

 a striking resemblance to Aiismads, ami perhaps h\ Pep| 

 to have a tendency to Arads. Menispermads maj 

 Sarsaparillas (Smilaceae), ami thus a connect 

 tyogens ; sfossweeds (Podostemacesa) maj he 

 Liverworts among Thallogens ; it is not unreal 

 as an exogenous form of A.rrow ■ , or Ca 

 Lemna, ami the whole Nymphal Allium. 

 Hydrocharads. 



The different methods of classifying I 

 tin- introductory part of this work. That which 

 on the following considerations. 



The office of reproduction i>. after that 

 essential in the economy of both plants and 



