422 MORPHOLOGY. 



is now compared with the developed leaf, we find that it exactly cor- 

 responds to the ligule. The cotyledon itself is also developed strangely, 

 expanding out as a flat lamina, not only upward and laterally, but also 

 downward (fig. 264, C. b. d.). Thus is formed the so-called scutellum, 

 to which, on account of its freely projecting bud, covered with an invest- 

 ment from the vagina, and its equally projecting radicle (fig. 264, c.), 

 the embryo appears to be adherent. The radical extremity is finally 

 perfected to a little cone ; as, however, it is never to be developed, the 

 rudiments of several adventitious roots (fig. 264, h.) are formed from 

 the base of the bud, at the point where it is connected with the coty- 

 ledon, therefore from the first node of the plant : these then, lying on 

 the parenchyma of the radicle, appear to be surrounded by a sheath* 

 (fig. 264, D. h.) 9 the true radicle. Then, in addition, it often happens 

 that the cotyledon arises into a kind of collar on both sides of the bud 

 and radicle, and thus more or less completely encloses them again, e. g., 

 in Zea Mays, which has been very incorrectly compared with the true 

 slit of the cotyledon. 



On the whole, abnormal modes of development of the embryo do not 

 appear to occur in such numbers in the Dicotyledons as in the Mono- 

 cotyledons ; the family of the Orontiacece especially certainly furnishes 

 wonderfully rich material for the discovery of most interesting facts ; 

 the forms of the embryos perfectly agree scarcely in any two species 

 of Pothos, and, if I am not very much mistaken, embryos with two or 

 three buds occur, e. g., in Pothos reflexa (fig. 260.) : on this point, how- 

 ever, my knowledge of the development is too imperfect for me to ven- 

 ture to speak. 



History, 



The first to whom we owe minute investigation of the Monocoty- 

 ledonous embryo, was C. L. Richard, in his Analyse du Fruit, 1808; 

 soon after that Robert Brown discovered (Prodr. flor. nov. Holl. 1810) 

 the slit of the cotyledons in the Aracece, Typhacece, and Naiadacece ; 

 he looked upon this, howeVer, as a peculiarity of these families, 

 and all botanists followed him. Mirbelf, in 1829, very indefinitely 

 indicated an analogy of the embryo of the Grasses and Liliacece. 

 Finally, in 1837, I J demonstrated, from the history of development of a 

 great number of Monocotyledonous embryos, not only that the slit of the 

 cotyledon, discovered by Rob. Brown, is universal, but also showed that 

 it must always exist, because it is the result of the true typical develop- 

 ment of the embryo. These observations were soon afterwards con- 

 firmed by Ad. de Jussieu in an interesting treatise, and the analyses 

 of some rarer and very aberrant embryos added. All that Link (El. 

 Phil. Bot.) says about the embryo is wholly worthless, because he evi- 

 dently has not observed the course of development of a single one him- 

 self, and therefore arbitrarily guesses at random of the individual parts 

 of the ripe embryo. 



169. 3. Dicotyledons. The embryonal globule in the Dico- 

 tyledons has sometimes rather a spherical and sometimes rather an 

 ovate form. I cannot decide whether it retains this form until the 



* Some therefore call the true radicle the root-envelope (coleorkiztt\ which is alto- 

 gether superfluous. 



f Mem. de 1'Acad. des Sc. 1836, p. 646. 



f Wiegm. Archiv. 1837, and A. L. C. N. C. vol. xix. p. 1. 



Sur les Embryons Monoc. Ann. des. Sc. Nat. June, 1839. 



