194 



FLOWEE-BUD — ^iESTIVATION. 



In these instances of aestivation, the parts of the verticils are con- 

 sidered as being placed regularly in a circle, and about the same height. 



Fig. 285. 



Fig. 286. 



Fig. 287. 



Fig. 288. 



Kg. 289. 



and they are included under circular aestivation.. But there are other 

 ca.ses in which there is a slight difference of level, and then the true 

 spiral arrangement exhibits itself. This is well seen in the leaves of 

 the calyx of Camellia japonica (fig. 289 c), 

 which cover each other partially like tiles on a 

 a house. This aestivation is imhricate. At 

 other times, as in the petals of Camellia (fig. 

 289^), the parts envelop each other completely, 

 so as to become convolute. This is also seen in 

 a transverse section of the calyx of Magnolia 

 grandiflora (fig. 291), where each of the three 

 leaves embraces that within it. When the 

 parts of a* whorl are five, as occurs in many 

 Dicotyledons, and the imbrication is such that 

 there are two parts external, two internal, 

 and a fifth which partially covers one of the internal parts by its 

 margin, and is in its turn partially covered by one of the external 

 parts, the aestivation is quincuneial (fig. 290). This quincunx is com- 

 mon in the corolla of Rosacese. Fig. 290 is a transverse section of 

 the calyx in the flower-bud of Convolvulus sepium, in which the parts 

 are iiumbered according to their arrangement in the spiral cycle, and 

 the course of the spiral is indicated by dotted lines. In fig. 292, a 

 section is given of the bud of Antirrhinum majus, showing the imbri- 

 cate spiral arrangement. In this case it will be seen, when contrasted 



Fig. 285. Diagram of calyx, c, and corolla, p, in the tad of Guazuma ulmifolia. .Sstiva- 

 tion of calyx valvate, of petals induplicate. Fig. 286. Diagram of calyx, c, and corolla, 

 p, in the flower-bnd of Alth^a, rosea. .^Estivation of calyx reduplicate, of petals contortive 

 or twisted. Fig. 287. Flower-bud of Althaea rosea in a young state, showing calyx, c, 

 still completely enveloping the other parts, and the edges of its divisions touching each 

 other. Fig. 288. The same in a more advanced state, where the calycine divisions, c, are 

 separated so as to allow the expansion of the corolla, the petals of which, p, are contortive 

 in {estivation. Fig. 289. Flower-bud of Camellia japonica. c. Imbricated sepals of the 

 calyx, p, Petals with convolute aestivation. 



