ITS POSITION IN RESPECT TO THE BRACT AND AXIS. 243 



the position of least pressure, and thus fall into these intervals with 

 all the exactness that is actually found in nature. For in these liv- 

 ing bodies, endowed as they are with plasticity and a certain pow- 

 er of adaptation to circumstances, the positions assumed are not 

 mathematically accurate ; and the effect of unequal pressure in the 

 bud in throwing the smaller parts more or less out of their normal 

 position may be observed in almost any irregular flower. More- 

 over, in all the forms of phyllotaxis from T 5 ^- onwards, it is doubtful 

 whether what we term vertical ranks are exactly superposed. In 

 tracing them onward to some extent, we perceive indications of 

 a curviserial arrangement, where the superposition is continually 

 approximated, but is never exactly attained. 



443. When, therefore, the floral circles consist of parts which 

 are evidently developed in the same horizontal plane (494), they 

 are most simply viewed as decussating verticils, as formed after 

 the manner of opposite leaves. When they are imbricated in the 

 bud (492), or show in other ways a spiral disposition of parts, we 

 may conceive that the law of alternation is conformed to in the 

 manner which Jussieu has suggested, or in some such way. How- 

 ever explained, we cannot fail to discern an end attained by such 

 arrangement, namely, a disposition of parts which secures the 

 greatest economy of space on an abbreviated axis, and the greatest 

 freedom from mutual pressure. 



444. Position of the Flower as respects the Axis and subtending Bract, 



All axillary flowers are situated between a leaf and the stem, or, 

 which is the same thing, between a bract and the axis of inflores- 

 cence. These two fixed points enable us to indicate the relative 

 position of the parts of the floral circles with precision. That part 

 of the flower which lies next the leaf or bract from whose axil it 

 arises is said to be anterior, or inferior (lower) : that which is 

 diametrically opposite or next the axis is posterior, or superior 

 (upper).* It is important to notice the relative position of parts in 

 this respect. This is shown in a proper diagram by drawing a 

 section of the bract in its true position under the section of the 

 flower-bud, as in Fig. 282 : that of the axis is necessarily diamet- 



* As if these were not terms enough, sometimes the organ or side of the 

 flower which looks towards the bract is likewise called exterior, and the organ 

 or side next the axis, interior; but these terms should be kept to designate the 

 relative position of the members of the floral circles in aestivation (490). 



