CATTLEYA LIBIATA. 



55 



Archipelago, and China ; but none have as yet been met with in Europe, Northern 

 Asia, New Holland, or Africa. 



In our fifth number (fol. 36) we made a few introductory remarks on the 

 natural arrangement of plants, showing that all flowering plants are divisible 

 into two distinct and well marked classes, namely, Exogens, or such as increase 

 inwardly, that is, by the deposition of woody fibre between the bark and the 

 outside of the stem ; and Endogens, or such as increase inwardly, that is, by the 

 deposition of woody fibre near the centre of the stem. Accordingly, in Exogens 

 we observe pith in the centre surrounded by distinct layers of wood, with rays 

 of cellular tissue extending from the centre to the circumference, and covered 

 externally by bark ; while in Endogens the woody fibre and cellular tissue being 

 mixed together in one uniform mass, present no distinctions of pith, wood, and 

 bark. A transverse section of an oak will exemplify the former ; of a cane the 

 latter. Exogens having for the most part two cotyledons or seed-lobes, are also 

 called Dicotyledons ; while Endogens having usually but one, are called Mono- 

 cotyledons. Of the net-like distribution of the veins in the leaves of Exogens, 

 and their arrangement in parallel lines in those of Endogens we have formerly 

 spoken ; to which may be added, that in Exogens the leaves are jointed with the 

 stem, while in Endogens their attachment with the stem is usually without arti- 

 culations. Finally, these groups are found to differ very materially in their mode 

 of germination. In Exogens the radicle is distinct and naked, commencing its 

 growth by simple elongation of its apex ; while in Endogens it is enclosed within 

 the solid, undivided embryo, which thus forms a case for its protection, and 

 through which it protrudes. Hence the celebrated Richard applied the terms 

 Exorhiz^: to the former, and Endorhizj3 to the latter, which literally mean 

 outward root and inward root. The seed of a Lupine placed in the ground for a 

 few days, and afterwards removed for examination when the process of germina- 

 tion has just commenced, will exemplify the former ; a seed of Narcissus may be 

 taken for the latter. It appears therefore, that although the terms Exogense, 

 Dicotyledones, and Exorhizse are applied indiscriminately to one division of 

 flowering plants, and Endogense, Monocotyledones, and Endorhizse to the other, 

 they are not strictly synonymous terms, inasmuch as each of them refers to a 

 particular fact. 



Having noticed the more important features by which Exogenous and Endo- 

 genous plants are distinguished, we proceed in the next place to the sub-classes, 

 groups, &c, into which they are divided. This has been effected in various ways 

 by different botanists, but to that proposed by Dr. Lindley we give a decided 

 preference. We confine ourselves on the present occasion to the Endogenous or 

 Monocotyledonous class, which are divided into 1. Epigynosce. — 2. Gynandrosce. — 

 3. Hypogynosce. — 4. Retosce. — 5. Spadicosce. — 6. Glumosce. Each of these groups 

 will form a subject for separate consideration. 



We confine ourselves on the present occasion to the group Gynandrosce, the 



