for the advance of Botany. 1 1 7 



occur. Perhaps we may be allowed to suspect]some analogy between 

 the primitive forms of crystals, and those normal or typical forms 

 which may be assigned to different species of plants, by the appli- 

 cation of such rules of morphology as already appear to a certain ex- 

 tent satisfactorily established, viz. the partial suppression or com- 

 plete abortion of particular organs, and the adhesion of others. Al- 

 though no precise laws have hitherto been discovered in botany, 

 which assign the limits of variation to a given species, some approxi- 

 mation to them might possibly be expected, by attending more strict- 

 ly than seems to have been customary to the principles of analogi- 

 cal reasoning. Thus, when we find the admitted varieties of one 

 species ranging through certain peculiarities of structure, it is rea- 

 sonable to suppose, that if we now find two other individuals of 

 the same genus, which do not differ more, or so much from each 

 other as the former two, then these ought also to be considered as 

 varieties of a single species. In the determination of species, our 

 most eminent botanists seem frequently to be acting against their 

 own judgment, and compelled to describe as distinct what they 

 have little or no doubt themselves, ought to be considered as identi- 

 cal. Hence they are perpetually qualifying their descriptions with 

 such phrases as these, " Priori nimis affinis," — " vix et ne vix dis- 

 tincta," — and even after this a third species is still described as 

 " duabus prioribus exacte intermedia I" It is perhaps extremely 

 difficult to form any decided opinion about the limitation of species, 

 and we find some persons who, instead of wishing to multiply them 

 beyond their due limits, are inclined to run to the opposite extreme, 

 and believe that there is no such thing as distinct species at all ; a 

 clear proof again that we are in want of multiplied experiments, 

 undertaken by careful and scientific observers. But we shall never 

 make any progress towards solving the problem, if we continue dis- 

 satisfied with the positive results of experiments, merely because 

 they happen to militate against our preconceived notions ; and 

 though a proper degree of caution ought always most unquestionably 

 to be exercised, before we admit even the most positive evidence in 

 favour of a new and startling fact, yet there can be very little value 

 assigned to any mere assertions which may be made contradictory 

 of such a fact, even though they should be partially supported by 

 the negative results of direct experiment. Although several years 

 have passed since Mr Herbert proved by experiment that numerous 

 varieties of Primrose, Cowslip, Oxlip, and Polyanthus, might origi- 

 nate from the seeds of a single plant, agreeably to the opinion of 

 Linnaeus, who considered them all to be mere varieties of the same 



