54 Mil. liENTHAM ON LOGANIACEJE. 



adopted for testing them, the greatest uncertainty has been the con- 

 sequence. Malvacece are connected with Tiliacece by numerous 

 genera which some would unite into one intermediate order, whilst 

 others consider them as constituting from two to six or seven in- 

 dependent ones, and others again propose uniting more or less of 

 these groups with Malvacece. The Mernecylece are in the eyes of 

 some botanists one or two intermediate families between Melasto- 

 macece and Myrtacece, whilst for others they are but a tribe of the 

 former. So it is with the connecting groups between Myrtacece and 

 Passiflorece, between the latter and Cucurbitacece, &c. Amongst 

 some of the largest and most universally recognized Monopetalous 

 orders the connexion is still more gradual and the limits proposed 

 more arbitrary. There can be no doubt that Bubiacece, Apocynece, 

 Gentianece, and Scrophularinece are large independent orders in- 

 dicated in nature, yet those genera now amalgamated under the 

 name of Loganiacece bind them so firmly together, that some of 

 these genera will be found even more closely allied to certain 

 others of each of the above orders respectively than they are to 

 each other. On the other side, ScropJiularinece themselves pass 

 imperceptibly into Solanece, Pignoniacece or Convolvulacece, and 

 through these into several others. 



Since the metaphor of a chain or linear series has been found 

 inadequate for the illustration of the connexion of the natural 

 groups, that of a geographical area or map has been more generally 

 resorted to. In following out this idea, we may compare the 

 natural system to an extensive country more or less densely 

 wooded. Here the Compositce, Leguminosce, and other well-defined 

 orders may be represented by dense forests clearly separated from 

 all others by open spaces all around them, although here and there 

 a solitary tree or a small cluster may stand a little out from the 

 general boundary-line. The Malvacece and Tiliacece, the Melasto- 

 Tnacece and Myrtacece, the Myrtacece and Passijlorce, these again and 

 the Cucurbitacece would not be separated by any clear open space, 

 but by a tract still wooded, but of less density, in which here and 

 there the trees would be so thinly scattered as almost to break the 

 connexion. So the above-mentioned Monopetalous orders, the Bu- 

 biacece, Apocynece, Gentianece, and ScropJiularinece would, be typi- 

 fied by large and dense woods rather widely separated from each 

 other, but the intervening space would be dotted over with solitary 

 trees or small clusters representing our Loganiacece. Many of these 

 may be very near to the surrounding woods, and considerable clear 

 spaces may intervene between some of them ; yet, in mapping out 



