AÎSÏHOCYAX IN THE TETALOID CALYX. ö 



Wlieii tlie flowers open tlie petaloid cmIvx jippeais not 

 absolutely wliite l)ut yellowish or slightly greenish, fading from 

 the base towards the end. However, this colour is not due to 

 the presence of chlorophyll, but to the slightly yellowish cell-sap. 

 At this stage protanthocyan is already formed and distributed 

 equally over the calyx-leaf by centrifugal propagation. (Fig. 2.) 

 After undergoing some morphological and metal)olical changes 

 from external influences (especially sunlight) the calyx becomes 

 glossy wdiite and red anthocyan now begins to appear. 



Microscopical Structure. — On cross section the upper and the 

 lower e])idermal cells show a similar Hat form and hold from 

 four to ten mesophyll (chlorophylless) cell-layers between them. 

 The mesophyll layer consists of more or less irregular, loosely 

 united cells, in intercellular space and contains crystals of calcium 

 oxalate. Crystals of irregular shape are very abundant in the 

 mesophyll and in the hypodermal pa its. Some raphides occur 

 in the middle part of mesophyll. 



Looked at fiom alcove, the upper ei)idermal cells show less 

 wavy outlines than tlie lower, and both are furnished with 

 indistinct cuticular striations. The lower epidermal cells are 

 provided with many stomata and deciduous unicellular hairs, 

 wdiich are covered with thick cuticular spots. The latter are 

 entirely wanting on the upper side. In this phase each cell in 

 the calyx-leaf contains besides protoplasma nothing but slightly 

 yellow sap, and the whole tissue is very clear. At a later period 

 this yellowish sap becomes much more conspicuous and is confined 

 to both epidermal cells. (Fig. 11.). This is the stage at which 

 protanthocyan passes into yellow anthocyan, tlie chemical reac- 

 tions of which are given in the following table I. 



