312' CONSIDERATIONS RESPECTING 



tally, present in a particular structure, or an important general law 

 respecting the influences which modify outward forms, and the circum- 

 stances which are common to them through all variations. 



Every specific type essentially consists in a certain association of 

 organs, constructed on a fixed plan, disposed in a definite order, 

 nourished equally or unequally, as the case may be, and subject to 

 different degrees of pressure on each other from causes which can, 

 often at least, be understood. Such elements, as the number of phy- 

 tons — whether one or two — forming the plant, the mode of provision 

 for its early nourishment, with or without albumen in the seed, the 

 natural order of the leaves, their peculiar venation, and mode of folding 

 in the bud, with the consequences of these, are constant and unchan- 

 geable, but it is easy to conceive that from abundance or deficiency 

 of nutriment, and from various causes, internal as well as external, the 

 equal development of the organs, and their nearness to each other 

 may 'be greatly affected. Now we certainly know that parts greatly 

 deficient in nutriment although rudiraentally present, remain undeve- 

 loped and are either not seen at a,ll or present an altered appearance, 

 and we know that whenever two vegetable organs are brought close 

 together, whether at their edges or by their whole surfaces, they be- 

 come connected by cellular tissue so as to form apparently one part. 

 Again, the whole of every vascular plant is made up of root, stem and 

 leaves, with their modifications. Flowers are only buds in which the 

 internodes are suppressed and the leaves are developed in a peculiar 

 manner to suit a special function. As therefore, in a great many 

 plants the extent to which leaves continue to be produced from one 

 bud is uncertain, we see the reason why the number of circles of parts 

 in a flower may vary, and it is obvious that increased or diminished 

 pressure of the circles on each other must affect both their magnitude 

 and their connection or separation, whilst peculiar pressure must tend 

 to reduce the number of parts in a circle, and animequal distribution 

 of the nutriment to enlarge some at the expense of others. There are 

 cases in which two or more buds originating near each other may be 

 united from their first production, and have their parts combined so 

 as to produce a composite branch or flower, the cause being the same 

 which produces the coherence of adjoining organs in one circle of a 

 flower. The distinction between the several parts of a flower is only 

 a difference of development, every leaf being in its origin capable of 

 assuming any of the forms. Of course when the whole or any portion 

 of one circle of parts assumes a different character from that which 



