PIIANEROGAMIA : FLOWERS. 



421 



end we then discover, in this transverse section, an adventitious root 

 (fig. 263, C. d.) still buried in the parenchyma, but already perfectly 

 determined, and even provided with a calyptra ; this, also nearly parallel 

 with the axis of the embryo, has its apex turned toward the micropyle ; 

 the axes of the bud and the adventitious root form an angle of scarcely 

 30 with their divergent apices. If we trace the development we see 

 that the bud originally forms the apex of the embryo, and is afterwards 

 gradually thus pushed aside by the growth of the cotyledon. The 

 course of development (which is analogous to that of Cyperacece) I have 

 traced so often in Lemna minor and trisulca, as well as in Telmato- 

 phace gibba, investigated so many ripe seeds of the three said plants, 

 and of Wolffia Delili, that I may venture to declare that nothing at all 

 corresponding, even distantly, to the analysis given by A. Brongniart* 

 occurs in the embryo of the Lemnacece ; how he obtained such strange 

 figures I cannot explain. 



The import of the individual parts of the embryo of Grasses, which 

 formerly gave botanists so much trouble, is exhibited most simply in 

 the course of development. In the Grasses the embryo is originally 

 formed exactly as in other Monocotyledons (fig. 264, A.) ; but the fol- 

 lowing variations subsequently appear. During the formation of the 

 vaginal portion the bud is also considerably developed, and thus that 

 part of the vagina covering it is pushed outward (fig. 264, B.), and 

 a papilliform process is gradually formed over the bud, becoming 

 blended, leaving only a slit : this process is usually regarded as the free 

 bud, not enclosed by the cotyledon (fig. 264, C. e.f.). But if this part t 



264 



* Arch, do Botanique, vol. ii. p. 97. (1833.) 



f Some name it with the superfluous term Coleoptile. 



tyledon ; c, plumule. B> Later condition: a, 6, c, as in A. The radicle is not yet 

 completely rounded ; the suspensor is removed ; the plumule is already partly enclosed 

 in the sheath of the cotyledon, and pushed downward. C, Perfect embryo in longi- 

 tudinal section: a, b, c, as in B; d, rudiment of an adventitious root. D, Perfect 

 embryo in longitudinal section at right angles to the preceding : a, b, c, as in B. 



164 Secale cereale. A, Very young embryo: a, rudimentary plumule; b, cotyledon ; 

 c, radicle. B, Later condition : a, b, c, as in A ; J, the expansion of the scutellum be- 

 ginning ; e, commencement of the formation of the vagina of the cotyledon, which 

 envelopes the plumule. C, Perfect embryo (not so much magnified as in A and .5) : 

 6, c, as in B ; d, cotyledon as scutellum ; e, vaginal part of the cotyledon ; /, slit of the 

 same ; h, /t, h, adventitious roots, still enclosed in the cortical portion. Z), Longitudinal 

 section of the former : a /, as in B and C ; g, adventitious root ; h, investment of it 

 formed by the cortical substance. 



