Organization in Phccnogamous Plants, 175 



of the stem and root, differing as they do, become intelligible. 

 During the second stage of the development the upper end 

 of the germ expands in a globular form, (fig. 6, 7, 11, 12, l^, 

 & 15,) and from the sides of this globular extremity, in dicoty- 

 ledonous plants, the two rudimentary cotyledons become de- 

 veloped as cellular projections, their points being more or 

 less free* (fig. 16 & 17). In these, as also in the stem it- 

 self, the elongated cells and spiral vessels are not formed 

 until a much later period : the mode in which this growth 

 takes place was in its principal features described with per- 

 fect accuracy by C. F. Wolff. In the monocotyledonous 

 plants, on the other hand, an asymmetrical elevation is form- 

 ed at the summit of the cylindrical embryo (fig. 8), which 

 ultimately constitutes the cotyledonous leaf surrounding the 

 stalk, and which also subsequently incloses more or less the 

 terminal bud {-plumula) f . This process offers the second and 

 greatest difference to which a plant can lay claim, namely, 

 the antagonism between vertical longitudinal formation and 

 horizontal superficial extension. 



All subsequent development of the plant, and every later 

 formed organ, are only modifications of these two portions of 

 the axis, the stem\ and of the lateral organs, the leaves. This an- 

 tagonism therefore appears to be something original; indeed 

 the axis is formed at an earlier period than the cotyledons, from 

 which may be seen the great error of that opinion which consi- 

 ders the stem to consist of adherent leafstalks, and the terminal 

 bud to be an axillary one, as for instance Agardh does. The 

 most important points of difference in the cotyledons are again 

 repeated in the leaves also, which are indeed only after-forma- 

 tions of those organs: thus for example we find in the Stapelice, in 



• Punctum vegetaiioniSf according to C. F. Wolff. 



f It will be seen from this descripdon of the process of development 

 that every monocotyledonous embryo possessed originally a plumula exserta^ 

 and that wherever this is inclosed, there must invariably be a fissure 

 present, however fine it may be. The grasses have been usually understood 

 to belong to the families with ^plumula exserta^ but quite incorrectly, since 

 the-phirmila in this family becomes ^er/ec^ by means of an elevation of the 

 cotyledon closed with the exception of a very fine slit (the outer closed 

 leaf of botanists), and this portion of the cotyledon, like every other 

 of its peculiarities, becomes repeated in the subsequent leaves in the 

 analogous formation of the ligula, whilst the scutelluvi^ constituting the 

 principal portion of the cotyledon, corresponds to the leaf itself. Some- 

 times the cotyledon folds itself together once more, as in Zea Mays,vih\ch. 

 formation has been falsely compared to the fissure of the cotyledon in the 

 Aroidecc'f or it sometimes forms on its anterior surface small protuberances, 

 which however cannot be considered as second cotyledons, since they are 

 in connexion with the axis at a point lower down than the cotyledon itself j 

 and a second leaf cannct possibly be formed beneath the earlier one. 



