248 Sir Edward Ffrench Bromhead on the Arrangement of 



Plants, no doubt, principally differ from each other in the 

 degree and peculiar mode in which the parts are developed, and 

 this without reference to the question whether they came sepa- 

 rately from the hand of the Creator with their parts in a cer- 

 tain state of development, or whether all have arisen from the 

 progress or regress of development in a hvf original types. Whe- 

 ther a system of radiation and branching be that of nature, or 

 whether several series arise from distinct types, the families must 

 probably, in the same stage of development of any structure, 

 shew a certain parallelism or relation, which would, under our 

 present indefinite views of affinity, sometimes cause them to be 

 placed together. It is also conceivable, if the development should 

 cease at any point, and a regress of structures occur in a modi- 

 fied degree and order, that a new set of relations would occur 

 among families not properly contiguous. To meet these diffi- 

 culties, it is clear that the opinion of no one botanist can be 

 tiifsted, and that very strong evidence of relation cannot alone 

 dv . ide whether the relation be one of affinity or correspondence. 

 Take for instance two parallel series, 



a, J, 6", J, &c. 



a; h; c; d; &c. 



and we may arrange these in apparent natural connection, 



fl, a,' 6,' b, c, c\ £?,' d, &c. 

 though the order is unnatural, and such as never could form a 

 foundation for drawing conclusions as to the physiological se- 

 quence. In an acute and accurate writer, I have found four 

 families, from four distinct corresponding series, placed in juxta- 

 position, and the fact speaks for the sagacity of the writer under 

 the circumstances of the science. But we are not wholly with- 

 out a clew ; — in the natural series all the adjoining families are 

 7 elated to each other ; in the parallel series the relation is in a 

 great measure limited to the families parallel, without strikingly 

 extending to the contiguous families. A great source of error 

 has been the endeavour io Jbrce together all the families which 

 show relation ; our course, on the contrary, should be to form 

 groups of families continuously connected, throwing aside those 

 which do not easily come in succession, for future inquiry, as 

 being probably parallel or of accidental resemblance. The fa- 

 milies so thrown aside will often most unexpectedly form them- 



