APPENDIX A 627 



ovules are curved, and seeds ex-albuminous (Fig. 477, I. II.). Fruit, a "siliqua" 

 which is a dry capsule, the lateral carpellary walls of which split from the 

 base upwards, leaving the two placentas as a frame with the transparent 

 septum stretched between them (Fig. 101). The septum is called "false' 

 because it is formed late, by ingrowths from the two opposite placentas, the 

 ovary being originally unilocular, as it is in the Poppies and in the Capers. 



Pollination. The flowers being grouped are conspicuous, and are visited 

 for their pollen, and for honey. The honey-secretion is by glands at the 

 insertion of the short lateral stamens. Insects passing from flower to flower 

 and inserting their proboscis, will probably effect intercrossing ; but self- 

 pollination is possible, and it is even provided for by the longer stamens 

 coming in contact with the stigma as the style elongates. It is not a highly 

 specialised type of flower. It is very constant in the Cruciferae, and may be 

 equally well studied in the Wallflower (20). The structure is probably di- 

 merous throughout, but with a fission of the median petals to form divergent 

 pairs, and of the median inner stamens to form the four longer. This is 

 expressed in the floral formula : — S. 2 + 2. P. 2., x , A. 2 + 2 2 , G. £2). 



The construction of the flower would then be theoretically as follows : 



Two antero-posterior sepals. 



Two lateral sepals. 



Two antero-posterior petals (by fission resulting in the four oblique petals). 



Two lateral stamens, short. 



Two antero-posterior stamens (by fission resulting in the four long stamens) . 



Two lateral carpels. 



Comparison with the Poppies and the Caper Family shows this to be the 

 probable interpretation of the Cruciferous Flower, and that it is thus referable 

 to a dimerous origin, with regularly alternating whorls. 



The Cruciferae provide a large proportion of garden vegetables, such as 

 Cabbage, Cress, Turnip, Horse-radish, etc. 



ORDER : GERANIALES. 

 Family : Geraniaceae. Example : The Field Geranium. 



(21) The Field Geranium (Geranium pratense, L.) is a strong- growing herb 

 with opposite, palmate, and stipulate leaves. The inflorescences are lax 

 cymose panicles (Fig. 478). Each flower consists of : 



Calyx, sepals 5, polysepalous, inferior. 



Corolla, petals 5, polypetalous, inferior, alternating with the sepals. 



Androecium, stamens 10, free, perigynous, with filaments widened at the base. 

 The five petaline stamens are external, the five sepaline are internal, a con- 

 dition described as "obdiplostemonous," and notable as an apparent departure 

 from the rule of alternation of successive whorls. 



Gynoecium, carpels 5, syncarpous, superior, with single style bearing five 

 distinct stigmas. Ovary with five loculi, each containing two ovules, of which 

 only one usually matures. 



The dry fruit is characteristic. The style remains as a firm woody beak. 

 At ripeness each carpel suddenly splits away longitudinally from the beak 

 and curving sharply, hurls out its seed to a distance (Fig. 243, p. 324). 



The floral formula is S. 5, P. 5, And. 5 + 5, G. 5. 



