i2i6 A TEXTBOOK OF THEORETICAL BOTANY 



seems, in these carpels, to determine the extent of their fertihty, since the 

 further up it extends itself, the shorter is the length of fertile carpel-margin 

 left in the closed structure. Either the sill or the carpel-margins may bear 

 the ovules, but not usually both. 



Some of the lower Monocotyledons show a carpel development which is 

 entirely non-peltate (e.g., Butomaceae) (Fig. 1 185). The carpel primordium, 

 like that of the monocotyledonous foliage-leaf, is not a hump but a horse- 



FiG. 1185.^ — Biitoniiis umbellatiis. Ontogeny of the flower. Showing non-peltate develop- 

 ment. A, B, C and D, Successive stages of carpel development. E, Interior of carpel 

 showing parietal distribution of ovules. (After Payer.) 



shoe and this shape is maintained throughout development, there being no 

 adaxial sill (Fig. 1186). The margins only cohere when the carpel is almost 

 fully formed, and even then not very firmly. 



Syncarpous ovaries may begin with a whorl of disconnected primordia 

 which develop independently until lateral growth brings their margins into 

 contact. From this point onwards growth becomes uniform all round the 

 whorl so that a ring-like wall arises, crowned by the apices of the originally 

 separate primordia (Fig. 1 187). Occasionally, however, the development of 

 each carpel proceeds individually, the lateral walls only cohering at a more 

 advanced stage. The most general condition is that of complete cohesion of 

 rudiments, from the beginning, so that the wall of the ovary arises and 

 progresses as a ring, especially in paracarpous ovaries, the position of the 

 joined carpellary margins being marked by internal folds in the ring. If 

 the mature ovary is septate, these folds extend themselves centripetally 

 and eventually unite at the centre, beginning from the base (where they 

 are often in contact with the axis or with each other from an early stage) and 

 progressing upwards. If, on the other hand, the ovary is paracarpous and 



