AITKXIHX A 



639 



than in flowers of more primitive construction. They are divided into two 

 series on the broad feature of the number of the whorls in which their parts 

 are arranged. Those with five whorls have the general formula, S. v, P. n, 

 A. n + n, G. n - , and they are styled the Pentacyclicae. Those with only four 

 whorls have the general formula, S. 11, P. n, A. n, G. n - , and they are styled 

 the Tetracyclicae. The number of the carpels is usually below the typical 

 number («). The number of the stamens is also frequently less than (>i) 

 or n + n, especially in those flowers where the pollination-mechanism is 

 specialised. 



(a) PENTACYCLICAE. 



ORDER : BICORXES. 



Family : Ericaceae. Example : Cross-leaved Heath. 



(33) The Cross-leaved Heath (Erica Tetralix, L.) is a shrubby moorland 

 plant, mycorhizic like the rest of the family, bearing minute stiff leaves, studded 

 with red, stalked glands. The margins of the leaves are reflexed, so that 

 the lower stomatal area is concave, and more or less closed. All these features 

 are xerophytic. 



Erica Tetralix. 



Fig. 491. 

 I. whole flower from outside. II. flower in section. 



III. floral diagram. 



The flowers are borne in dense racemes, and are pendulous on pedicels 

 bearing two bracteoles (Fig. 491). They consist of : 



Calyx, sepals 4, polysepalous, inferior, glandular. 



Corolla, petals 4, gamopetalous, inferior, globose, with a narrow opening, 

 through which the capitate stigma projects. 



Androecium, stamens 4+4, free, hypogynous, with curved filaments; 

 anthers dehiscing by two distal pores, which face downwards. From the base 

 of each anther two divergent spurs project outwards to the inner surface of 

 the corolla. 



b.b. 2 s 



