6 DR. HOOKEE AKD DE. THOMSON S PRiECURSOTlES 



the limits of such a group as Codonopsis and its allies ; and 

 although, in accordance with M. DeCandoUe's views, we have now 

 raised these subgenera to the rank of genera, we have by no 

 means altered our opinion of their relationship, and still less of 

 their structural peculiarities. Indeed we have little doubt that, 

 could we undertake a revision of the whole Order, these and many 

 other of the present genera would be reunited as subgenera of 

 larger groups. 



Upon this subject we take the liberty of reading a note on the 

 principles upon which genera should be established in Botany, 

 communicated to us by Mr. Bentham, who has kindly embodied 

 the views which we hold in common with him, in a memorandum* 

 appended to this communication. 



The genera of Campanulacece are indeed, for the most part, quite 

 artificial ; and of this the best proof we can offer is to be found in 

 the study of those already founded, and especially of the allies of 

 Codonopsis. These include plants so nearly connected by natural 

 characters of habit, colour, odour, and habitat, as well as by the 

 structure of their flowers, that their close affinity has never been 

 doubted ; but some of them present more striking differences from 

 one another, and more remarkable deviations from the common 

 plan on which the Order is constructed, than any other plants in it. 

 By far the greatest peculiarity is exhibited by Oampanvmoea and 

 Cyclocodon, genera which present the paradox of a cah/x inferus 

 and a corolla stipera. In Cyclocodon this anomaly is carried to 

 the highest degree, the sepals being in C. parviflorum placed on 

 the peduncle of the flower, far removed from the base of the 

 corolla and ovary, whilst in C. truncatum and in Campanumoea 

 they adhere to the base of the tube of tlie corolla. So remote 

 from one another are the points of insertion of the calyx and 

 corolla in both these instances, that the sepals have been de- 

 scribed as leaflets of an involucre, though their development is 

 opposed to this conclusion, and their aestivation is normally val- 

 vate. In Codonopsis the calyx is adherent to the base of the 

 ovary, and the corolla is inserted at the point where the lobes 

 of the calyx are given off : but so similar in other respects is one 

 species of this genus to one of Campanumoea, that they can with 

 difficulty be distinguished, except by a close comparison : and both 

 these last-named genera again differ wholly from Cyclocodon in 

 their ramification, large tuberous roots, twining stems, and foetid 

 milky juice. 



* See p. 30 of this vohime. 



