144 RANUNCULACE.E : ACERACE^E [CH. 



So far I have selected for our types flowers of 

 simple structure arid as compared with the more perfectly 

 differentiated flowers of the Buttercup, Rose, Laburnum, 

 Honeysuckle, &c. of imperfect composition. 



We will now examine one or two examples of the 

 more highly specialised floral types, so well known owing 

 to the aesthetic beauty of their coloured or conspicuous 

 perianth or corolla. 



The Buttercup, already described on p. 129, affords us 

 an excellent example of a complete actinomorphic, poly- 

 petalous flower, with hypogynous stamens and corolla, 

 and apocarpous pistil ; and the stamens and carpels at 

 least are spirally arranged acyclic. Its floral formula 

 runs as follows: 



K t G s A. &.. 



The Clematis affords another example of the same 

 type, with the difference that it has only one whorl of 

 petal-like non-essential organs. This perianth is really 

 a calyx ; there is no true corolla developed. 



The flowers of the Sycamore (Fig. 42) and Maples, 

 Aceracece, afford us examples of a new structure, inter- 

 posed as a fleshy ring-like cushion or wall of tissue around 

 the floral axis at the base of the calyx, and between it 

 and the stamens : this ring of tissue is known as the disc, 

 and many authors separate off the Natural Orders bearing 

 such a disc in their flowers from the Thalamiflorae, as the 

 Disciflora3. We may term it the Discifloral type. 



Careful examination of a flower of the Sycamore shows 

 that while the calyx of five separate sepals, and the 

 corolla of five separate petals alternating with them are 

 actinomorphic, the stamens are only eight in number, 

 the posterior one and the anterior one being absent ; and 

 the ovary consists of two carpels only placed antero- 

 posteriorly, and consequently the androecium and pistil 



