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Scientific Intelligence. 



yet it is still between those two genera that the limits are placed by tfm-* 

 versal consent ; so are they as irrevocably fixed between the closely 

 allied genera Teucrium and Vitex, which form the connecting link be- 

 tween Labiatce and Verbenacece. The vast orders of Umbelliferce and 

 Composites are equally isolated, notwithstanding the anomalous inflores- 

 cences of Horsfieldia and some others in the former, and of Xanthium in 

 the latter, which at first sight disguise their characters. The few species 

 of Apostasiece are but anomalous Orchidece, rather explaining their struc- 

 ture than connecting them with any particular order. Cyperacece and 

 Graminece retain their typical structure through all the singular modifi- 

 cations hitherto observed. 



" There are other orders again, even amongst the most numerous in 

 species after the Compositce and Legurninosce, which are admitted on all 

 sides to be natural, but upon whose precise limits few botanists can be 

 made to agree, an almost continuous chain of intermediate groups con- 

 necting them with adjoining ones. Here the severance has generally 

 been made wherever the links have appeared the weakest ; but as these 

 weak points have been variously appreciated by different minds, and no 

 definite standard has been adopted for testing them, the greatest uncer- 

 tainty has been the consequence. Malvaceae 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 inde- 

 pendent ones, and others again propose uniting more or less of these 

 groups with Malvacece. The Memecylece are in the eyes of some botanists 

 one or two intermediate families between Melastomacece and Myrtacece, 

 whilst for others they are but a tribe of the former. So it is with the 

 connecting groups between Myrtaceoe and Passiflorece, between the latter 

 and Cucurbitacece, &c. Amongst some of the largest and most univer- 

 sally recognized Monopetalous orders the connexion is still more gradual, 

 and the limits proposed more arbitrary. There can be no doubt that 

 Mubiacece, Apocynece, Gentianece, and Scrophularinece are large independ- 

 ent orders, indicated in nature, yet those genera now amalgamated under 

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

 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, 

 Scrophularinece themselves pass imperceptibly into Solanece, Bignoniacece 

 or Convolvulacece, and through these into several others. 



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

 quate 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 exten- 

 sive country more or less densely wooded. Here the Compositce, Legu- 

 rninosce,, 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 Melas- 

 tomacece and Myrtacece, the Myrtacece and Passiflorece, 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 



