ESTIVATION. 79 



called irregular, as tho pea, catmint, violet, aro regular, like other flowers, in the 

 early bud ; that is, the several petals aro at first seen to bo precisely similar, becom- 

 ing dissimilar and distorted in their after growth ; so in the stamens and other or- 

 gans. 



380. Cases in artificial development or teratology (jipa, a monstrosity, 

 Aciyof), where organs of one kind are converted into those of another kind by cul- 

 tivation, afford undeniable evidence of the doctrine in question — the homology of 

 all the floral organs with the leaf. Such cases are frequent in the garden, and bow- 

 ever much admired, they are monstrous, because unnatural. In all double flowers, 

 as rose, posony, Camillia, the stamens have been reconverted into petals, either 

 wholly or partially, some yet remaining in every conceivable stage of tho transition 

 In the double butter-cup (242) the pistils as well a3 stamens revert to petals, and iu 

 the garden cherry, flowering almond, a pair of green leaves occupy the place of the 

 pistils. By still further changes all parts of the flower manifest their foliage affini- 

 ties, and the entire flower-bud, after having giveu clear indications of its floral char- 

 acter, i3 at last developed into a leafy branch. (Fi jr. 243.) 



381. In Clarkia, Celastrus, damask rose, and other garden plants, cases have 

 been noted wherein tho petal asserts its foliar nature by producing a secondary 

 flower-bud in its axil ! Thus in a thousand instances of abnormal growth, we find 

 evidence proving the leaf to bo tho typo whenco all other forms of appendages aro 

 derived, and whither all tend to return. 



382. Further evidence of this view, equally conclusive, is found in the essen- 

 tial agreement of the aestivation of the flower-bud with tho phyllotaxy of tho branch. 



ESTIVATION. 



383. Definition — importance. This term (from ccstlvus, of sum- 

 mer) refers to the arrangement of the floral envelops while yet in tho 

 bud. It is an important subject, since in general the same mode of 

 aestivation regularly characterizes whole tribes or orders. It is to the 

 flower-bud what vernation {vermis, spring) is to the leaf-bud. 



384. Tiie various modes op aestivation are best observed in sections of tho 

 bud made by cutting it through horizontally when just ready to open. From such 

 ecctions our diagrams are copied. 



385. Separately considered, we find each organ here folded in 

 ways similar to those of the leaf-bud ; that is, the sepal or the petal 

 may be convolute, involute, revolute., etc, terms already defined. 



386. Collectively considered, the aestivation of the flower occurs 

 in four general modes with their variations ; the valvate, the contorted, 

 imbricate, and plicate. 



387. In valvate estivation the pieces meet by their margins with- 

 out any overlapping ; as in the sepals of the mallow, petals of Hydran- 

 gea, valves of a capsule. The following varieties of the valvate occur : 



388. Induplicate, where each piece is involute ; i. e., has its two 

 margins bent or rolled inwards, as in Clematis ; or reduplicate, when 

 each piece is revolute — having its margins bent or rolled outwards, as 

 in the sepals of Althea rosea. (Figs. 245, 246.) 



