INTRODUCTION. xxvii 



2. All modifications of either are respectively important, in proportion 

 to their connection with the phenomena of hfe. 



3. If we allow ourselves to be steadily guided by these considerations, 

 we shall find that the internal or anatomical structure of the axis, and of 

 the fohage, is of more importance than any other character ; because 

 these are the circumstances which essentially regulate the functions of 

 growth, and the very existence of an individual. 



4. That next in order is the internal structure of the seed, by which the 

 species must be multiplied. Thus the presence of an embryo, or its absence, 

 the first indicating a true seed, the latter a spore, are most essential cir- 

 cumstances to consider. And so also the existence of albumen in abundance 

 round the embryo, or its absence, must be regarded as a physiological 

 character of the highest value ; because, in the former case, the embryo 

 demands a special external provision for its early nutriment, as in oviparous 

 animals ; while, in the latter case, the embryo is capable of developing by 

 means of the powers resident in itself, and unassisted, as in viviparous 

 animals. 



5. Next to this must be taken the structure of the organs of fructification, 

 by whose united action the seed is engendered ; for without some certain, 

 uniform, and invariable action on their part, the race of a plant must become 

 extinct. Thus we find that the structure of the anthers, placentae, and 

 ovules, are more uniform than that of the parts surrounding them, while 

 their numbers are variable ; and the condition of the filament, w^hich appears 

 of so little importance in a physiological point of view, is also inconstant. 

 So also the textm-e and surface and form of the pericarp, which acts as a 

 mere covering to the seeds, is not to be regarded in these inquiries, and, in 

 fact, difi'ers from genus to genus ; as, for instance, between P}tus and 

 Stranvsesia, or Rubus and Spiraea, in the truly natural Rosaceous Order. 



6. On the other hand, the floral envelopes seem to be unconnected with 

 functions of a high order, and to be designed rather for the decoration of 

 plants,, or for the purpose of giving variety to the aspect of the vegetable 

 world ; and, consequently, their number, form, and condition, presence or 

 absence, regularity or irregularity, are of low and doubtful value, except 

 for specific distinction. There seems, indeed, reason to expect that every 

 Natural Order will, sooner or later, be found to contain within itself all the 

 variations above alluded to. Even in the cases of regularity and irregularity 

 we already know this to be so ; witness Veronica and Scoparia in Figworts, 

 and Hyoscyamus in Nightshades, Delphinium in Crowfoots, and Pelargo- 

 nium in Cranesbills. 



7. The consolidation of the parts of fructification is a circumstance but 

 little attended to in a general point of view, except in respect to the corolla ; 

 but as it seems to indicate either the greatest change that the parts can 

 undergo, or, where it occurs between important and usually unimportant 

 organs, that in such cases the latter become essential to the former, it pro- 

 bably deserves to be regarded with great attention. For instance, the 

 presence or absence of the corolla is often a point of little moment, and is, 

 we know, a very fluctuating circumstance. This is especially true of those 

 Natural Orders in which the stamens and petals are separated ; as in Rose- 

 woi-ts, Rhamnads, Onagrads, &c. On the other hand, when the stamens, 

 which are indispensable organs, adhere to the petals, the latter are more 

 constantly present, as in Figworts, Acanthads, Nightshades, <fcc. 



There are also certain other principles which experience tells us the 

 systematist must keep in view ; and most especially that of regarding of 



