TRANSLATIONS AND SELECTED ARTICLES. 223 



that part are maintained constantly vegetation and the formation of 

 new fibres [vascular bundles], which push outwards continually the 

 previously existing fibres, " hence these latter are at length so closely 

 packed against each other that they appear no longer to yield to the 

 effort of vegetation which would press them out to the circumference.'* 

 Adopted by botanists in general, this theory received an important 

 consecration when De Candolle founded on this character his division 

 of [the higher] vegetables into Endogens and Exogens. Notwith- 

 standing that the labours of MM. Mohl, linger, Mirbel, &c., have 

 since more than sufficiently demonstrated that these plants are not 

 really Endogenous, there remains a fundamental difference between 

 the structure of the stems of the two sub-kingdoms of Cotyledonous 

 plants. 



The anatomical researches in relation to Monocotyledonous plants, 

 although already very numerous, have not 'extended to a sufficient 

 variety of families to enable us to form, a precise judgment on the 

 assistance which anatomical knowledge might afford in respect to the 

 division of the sub-kiugdom into classes and families. We know, 

 however, that in this view the Liliacese, especially Dracaena and 

 Cordyline, differ from the Palms, which have generally been assumed 

 as the type. We also know that the fistulose culm of Graminaceae 

 offers remarkable peculiarities in the disposition of its fibres, especially 

 in respect to their crossing one another at the knot. Finally, it has 

 been more recently ascertained that the Orchidaceee, especially in 

 their appendicular parts, have anatomical elements exhibiting a special 

 structure. 



The immense sub-kingdom of Dicotyledonous plants has given 

 occasion to a much greater number of researches, of which we can 

 already, to a certain extent, appreciate the results. It is no longer 

 permitted to a botanist to consider all the plants as having identical 

 interior arrangements, and to give, for example, the stems of certain 

 Amentacese as a type to which they all conform. It is, on the con- 

 trary, extremely probable that these stems, whilst preserving some- 

 thing of a common type, and presenting some characters which be- 

 long to the whole sub-kingdom, display in their structure, according 

 to the families to which they belong, extensive variations both in the 

 intimate structure of the constituent elements taken separately, and 

 in the arrangement in relation to each other of these elements so as to 

 constitute the complete vegetable. 



