SPECIAL MORPHOLOGY: PHANEROGAMIA. 213 



X. XL MONOCOTYLEDONS AND DICOTYLEDONS. 



120. In the development of the pollen-tube into the embryo, 

 an essential distinction arises, according as there is formed one first 

 leaf (cotyledon) growing up from the whole circumference of the 

 rudimentary stem, or two or more first leaves, which collectively 

 embrace the stem, all on the same level. On this depends the dis- 

 tinction of Monocotyledons and Di- or Polycotyledons, with which 

 is connected many other essential peculiarities ; for instance, that of 

 the closed vascular bundles which are peculiar to the former, and 

 the unlimited bundles of the latter. Since, however, the dis- 

 tinction of the two groups can only be established in so few parts at 

 this stage of our inquiries, it is better, to avoid repetition, to treat 

 both together as Phanerogamic in the order of their individual 

 organs. 



With all its correctness, I hold the division of the Phanerogamia into 

 Monocotyledons and Dicotyledons to be but provisional. A perfect 

 morphological system will certainly first necessitate the distinction of 

 Gymnosperms and Angiosperms. The former without germens (and 

 mostly with homogeneous wood), comprehending the Conifer^ Cycadacece, 

 Loranthacece, and Gnetacece(?) ; the latter with the young fruit in the 

 form of a germen (and mostly heterogenous wood), separating into 

 Monocotyledons and Dicotyledons. At present, however, our knowledge, 

 so generally imperfect in reference to the majority of points connected 

 with the course of development, does not allow of this division being es- 

 tablished and carried out with any completeness. 



121. It will be universally admitted, that in its formation, every 

 Phanerogamous embryo attains to a stage in which it appears 

 within the cavity of the seed-bud as a little round or ovate body, 

 homogeneously composed of cells, and in which distinctions neither 

 of organ nor structure are to be discriminated. To start from this 

 condition, as a perfectly certain element, is sufficient, but it is 

 necessary to go back quite to this point to acquire a comprehension 

 of the fully formed embryo and the entire plant. This little body 

 forms all the cells, through which it grows and developes, inside 

 its own proper boundaries ; no organic parts are added from with- 

 out ; it is, therefore, the entire plant in its simplest rudiment. 

 The central portion first ceases to produce new cells; below (where 

 the pollen-tube penetrated the seed bud) and above (the point op- 

 posite the former) the formation of cells, and with it the deve- 

 lopment, proceeds, but in various ways and naturally opposite 

 directions. Below (the radical extremity) the embryo elongates 

 into a more or less conical point, the radicle (radicula). Above 

 (the cauline extremity) we find the following : the apex elongates 

 in a direction opposed to the rootlet, by the formation of new cells, 

 in such a manner that part of the new cells are constantly applied 

 upon the old ones, while part recompose the extreme point as 

 formative cells. At a variable distance below the apex there is a 



F 8 



