APPENDIX A 525 



Fruit, a flattened oval body, which matures dry. When ripe it splits into 

 two halves (mericarps), attached at first by a slender middle column, from which 

 they later break away, and are readily carried by the wind. Each mericarp 

 contains a single albuminous seed, and is marked by elongated oil-glands, four 

 on the outer and two on the inner flattened sides. 



Pollination. The aggregate inflorescence attracts the attention of insects 

 from a distance : the slight zygomorphy increases its effect. It is visited by 

 various insects, the exposed honey being accessible alike to short-tongued 

 and long-tongued. The individual flowers are protandrous, the stamens often 

 falhng before the stigmas are mature. Cross-pollination is probable by insects 

 crawling from flower to flower, but self-pollination is still possible. 



There is in the Cow Parsnip, but still more in other Umbelliferae, a partial 

 separation of the sexes in space as well as in time ; since the pistil is 

 degenerate in the later-formed flowers, they are practically male. That 

 is seen markedly in Astrantia and in Myrrhis. The condition is described as 

 andro-diclinous, and clearly it will promote cross-pollination, while it also 

 secures the pollination of those hermaphrodite flowers which arc formed 

 late, and are protandrous. 



DICOTYLEDONEAE—SYMPETALAE. 



Those Dicotyledons which have their petals united, that is sympetalous or 

 uamopetalous, are held to show in this respect a position in advance of the 

 Polypetalous types. A further character which they have in marked degree 

 is that their flowers are strongly cyclic, and the number of parts more definite 

 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. w, P n, 

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

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

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

 number (w). The number of the stamens is also frequently less than (>/), 

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

 specialised. 



{a) PENTACYCLICAE. 



ORDER : BICORNES. 

 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 rcflexcd. so that 

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

 are xerophytic. 



The flowers arc borne in dense racemes, and arc penduUnis on ixxlieels 



bearing two bracteoles (lag. ^33). They consist of 

 Calyx sepals 4, polysepalous, inferior, glandular. 



