oo 



EXTERNAL CONFORMATION OF PLANTS. 



consequence a large number of flowers (exogenous lateral shoots). In the nearly 

 related genus Dorstenia the fig remains open ; the margins of the tabular part of the 

 axis which bears the small flowers do not arch over and unite. 



Fig. 151.— Development of the fig of Finis carica (after 

 Payer: Organogenic de la fleur). 



Fig. 152. — Development of the flower oi Rosa alpiiia (after Payer: 

 Organogenic de la fleur). 



On a process very similar to the formation of the common fig depends the origin 

 of perigynous flowers and of inferior ovaries. Fig. 152 represents this in the perigynous 

 flower of a rose. I shows the very young shoot which is to develope into a flower, seen 

 half from above and from the outside ; the end of the shoot is thickly swollen ; it has 

 already produced the five sepals //, and the five petals alternating with them are visible 

 as little knobs, f, between which the apical region of the floral axis appears broad and 

 flat. While the sepals grow quickly, the zone of the tissue of the axis out of which 

 they spring becomes elevated in the form of a circular wall x in 77, which afterwards 

 contracts the opening above as seen in IV; an urn-shaped structure is thus formed 

 which is known under the name of a hip, and is distinguished when ripe by its red 

 or yellow colour and its sweet pulpy tissue. Here also the apical point lies in the 

 middle of the bottom of the hollow, and the inner surface of the wall of the urn is 

 a portion of the outer side of the floral axis which has been turned in. To this 

 corresponds the acropetal succession of the leaves (which, however, is only adhered to 

 in a general way). It is clear that if the apical point lies at y (in //), the succession 

 of leaves (in this case stamens st and carpels k) from above downwards must be termed 

 acropetal. 



If an additional proof of what has just been said were wanted, it would be fur- 

 nished by the history of development of the flowers of Geum, a genus very nearly 

 related to the rose (Fig. 153). That part of the floral axis which bears the sepals /, 

 the corolla c, and the stamens a a, is elevated in the form of a circular wall y y; but 

 the apical region which in Rosa entirely ceases to elongate, becomes again elevated 



