GENERIC DISTINCTIONS. Wl 



borus and Nigella also, by their tubulose nectaria ; . . .in Pan- 

 cratium the stamina are inserted in the nectarium, which distin- 

 guishes it from Narcissus ;...in Hyoscyamus, there is a covering 

 to the capsules, by which it i3 known from Physalis ;...the Re- 

 seda has always a lateral nectarium, but varies in its corolla and 

 pistillum the Campanula ban a quinquevaked nectarium, but 

 is inconstant in the corolla and capsule;... and lastly, the Iris has 

 a stigma of singular construction, but varies in the beard of its 

 corolla. 



There is, however, no one part or fructification that can be re- 

 lied on as a constant characteristic mark for all genera ; it being 

 found, that the part which is constant in some genera, will be 

 inconstant in others; thus in Caric a the flowers of the male 

 plant are monopetalous, and those of the female pentapetalous 

 in Myrica some species have naked seeds, others berries ;...m 

 Fraxinus some have a naked flower, and others a corolla ;., An 

 Geranium some have regular corolla, and others irregular;... in 

 Linum some are pentapetalous, others tetrapetalous ;... in Aconi- 

 tum some are tricapsular, and others quinquecapsidar and in 

 Trifolium some are monopetalous, others polypetalous ; some zr/o- 

 nospermous, and others polyspermous. 



This inconstancy of particular parts in many genera has been 

 another source of error amongst the earlier botanists, who have 

 parted many plants from their congeners on this account. Of 

 these mistakes we shall give an ample list in Chap. XXXII. 



When the characteristic mark of any genus is wanting in any 

 particular species, we should proceed with caution, lest we con- 

 found genera that should be distinguished : for want of this cau- 

 tion the Erica and Andromeda had been joined, but were part- 

 ed afterwards on account of the two horns in the anthem of the 

 Erica the Adonis had been joined to the Ranunculus, but 

 was parted from it again, on observing that it wanted the nectari- 

 ferous pore, ;...and the Aloe and Agave had been blended, till 

 it was observed that in the latter the stamina were inserted in the 

 corolla, and not in the receptacle. 



When the characteristic mark of any genus is observed 



