ENDOGENS. 95 



CLASS IV.— ENDOGENS. 



Monocotyledones, ./;«5. Gc«. 21. 1789) ; Desf. Mem. Inst. 1. 478. (1796). Endorhizese, Rich. Anal. 

 (1808). Monocotyledoneae oj- Endogente, DC. Th^orie, 207. {IS13). Meisner, p. 353. Cryptocoty- 

 ledoneae or GTa.m{eTSE,Aijardh. 73. (1821 j. — Amphibrya, E)idl. Gen. p. 76.— Teleophyta, Schleiden. 



Having now passed in review the absolutely sexless plants, called Thallo- 

 gens, and all that class which, under the title of Acrogens, comprehends a 

 numerous race among whom the existence of a double sex is conjectured 

 to exist, and having, moreover, disposed of the cm-ious Rhizogens, which, to 

 a fungal mode of growth join a complete sexual apparatus, we pass to 

 Endogens, or Monocotyledons. 



Here we find a vast multitude of species, with extremely diversified habits, 

 among whom occurs every attribute supposed to be connected with the most 

 perfect stmcture. Leaves and stems are distinctly separated ; spiral vessels, 

 breathing-pores, and sexes, are in a condition that admits of no further com- 

 plication ; and we find in the great majority everything which constitutes as 

 elaborate an arrangement of parts as we have any knowledge of in the 

 vegetable kingdom. 



This great class bears the name of Endogens, in consequence of its 

 new woody matter being constantly developed in the first instance towards 

 the interior of the trunk, only curving outwards in its course downwards. 

 That palm-trees grow in this way was known so long since as the time of 

 Theophrastus, who distinctly speaks of the difi'erences between endogenous 

 and exogenous wood.* But that this peculiarity is also extended to a con- 

 siderable part of the vegetable kingdom is a modern fact, the discovery of 

 which we owe to the French natm*alists Daubenton and Desfontaines. The 

 path being thus opened, the inquiry has subsequently, and more particularly 

 of late years, been much extended, and the result is the conviction that all 

 those numerous races to which Jussieu applied the name of Monocotyledonese, 

 agree essentially in this manner of growth. We may take the palm-tree as 

 typical of the endogenous structure. Li the beginning the embryo of a 

 palm consists of a cellular mass of a cylindrical form, very small and not at all 

 divided. As soon as germination commences a certain number of cords of 

 ligneous fibre begin to appear in the radicle, deriving their origin from the 

 plumule. Shortly afterwards, as soon as the rudimentary leaves of the 

 plumule begin to lengthen, spiral and dotted vessels appear in the tissue in 

 connection with the ligneous cords ; the latter increase in quantity as the 

 plant advances in growth, shooting through the cellular tissue, and keeping- 

 parallel with the outside of the root. At the same time the cellular tissue 

 increases in diameter to make room for the ligneous cords (or woody bundles, 

 as they are also called). At last a young leaf is developed with a consider- 

 able number of such cords in connection with its base, and, as its base passes 

 all round the plumule, these cords are consequently connected equally with 

 the centre which that base surrounds. Within this a second leaf gradually 

 unfolds, the cellular tissue increasing horizontally at the same time ; the 

 ligneous cords, however, soon cease to maintain anything like a parallel 



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 ufecvia-Tieav, oloVj'EXoctM, Uu^o;' cv ya.^ iamv cKfo^ia-^iyviv ovtoi Xoc^tiv' uXXoc xcit (f(x,<ri rnis^ov xcto, re f^iffoi^ 

 ocXXk xocroc to Toii 'ixuy, oIktti u.r, iTvoci ror/iv M^i<rt/.ivof hio Kcti hit*, ov V av Se'|s(fv oXm iXiiV uri/ xa.t tou 

 ^onixe? oi/iif^ix (fetinrot,! hioKfe^a. xetr cvhiv. Tkeophr. Hist. I. 8. 



