Dr. Lindley^s Natural System of Botany. 297 



And finally, their vascular system is very imperfect compared with 

 that of other Exogens of an equal degree of development. 



The other group, called Rhizantha, is far less correctly known, 

 but it seems to stand as it were between Endogens and Acrogens 

 of the lowest grade ; agreeing with the latter in the absence or very 

 imperfect state of the vascular system, in a general resemblance to 

 Fungi, and in the apparent seeds being mere masses of sporules ; 

 but apparently according with Endogens in the ternary number of 

 their floral envelopes, and in the presence of fully developed sexes. 



" Certainly there is no possibility of obtaining such important pri- 

 mary groups as these by any kind of artificial contrivance." — {Pre- 

 face, p. X. — xii.) 



The grand natural divisions of the vegetable kingdom are, there- 

 fore perfectly obvious, and may be very clearly defined. With our 

 present knowledge of vegetable structure no great difficulty is expe- 

 rienced in characterizing the orders or natural families, and all sub- 

 ordinate groups. The great desideratum has ever been to effect 

 such an arrangement of the orders under the primary classes, that 

 each family should be placed next to tiiose which it most nearly re- 

 sembles. This might easily be accomplished, if the idea once so 

 strongly insisted upon by poets and metaphysicians, of a chain of 

 beings, a regular gradation, by a single series, from the most perfect 

 and complicated to the most simple forms of existence, had any 

 foundation in truth. On the contrary, nothing is more evident, 

 than that almost every order, or other group, is allied not merely to 

 one or two, but often to several others, which are sometimes widely 

 separate from each other; and, indeed, these several points of re- 

 semblance or affinity, are occasionally of about equal importance. 

 A truly natural lineal arrangement is therefore impracticable, since 

 by it only one or two out of several points of agreement can be indi- 

 cated. As this method is, however, the only one that can be fol- 

 lowed in books, all that can be done is to arrange the orders in such 

 a manner as to offer the least possible interruption to their natural 

 affinities. The number of orders is so large that practical conveni- 

 ence seems to require their arrangement into groups subordinate to 

 the primary classes ; and when manifestly natural assemblages can- 

 not be recognized, we are obliged to employ those which, being less 

 strongly marked, and distinguished by a smaller number of charac- 

 ters, are apparently of a more artificial nature. The arrangement 

 employed by the learned Jussieu, in his celebrated Genera Planta- 



VoL. XXXII.— No. 2. 38 



