THE STYLE AND STIGMA. 397 



passing out of lateral union, or else provided with swollen side 

 walls, between which the pollen-tubes can easily grow downwards. 

 In either case a valuable conducting tissue for the pollen-tubes is 

 provided (compare p. 387). 



Pistil of Primula. Another free or superior ovary exists 

 in the flowers of the species of Primula (Primrose, Auricula, 

 Cowslip, etc.). These are dimorphic, i.e., have short-styled 

 and long-styled ovaries, and stamens inserted high up or low 

 down upon the tube of the corolla. A median longitudinal section 

 through the ovary shows us that the floral axis is prolonged 

 into the cavity of the ovary, and here enlarges into a mushroom- 

 like swelling. On grounds of comparative morphology, how- 

 ever, it is believed that this central structure is a part of the 

 carpellary leaves which adheres to the floral axis. At its apex 

 this swelling projects, papilla-like, into the pollen-passage of the 

 style. The entire surface of this swelling is covered with ovules. 

 We have here a free central placenta. The wall of the ovary is 

 in no way directly connected with this placenta. We can be quite 

 convinced of this by cross-sections in which the wall of the ovary 

 appears as a free ring around the central placenta, or, if an equa- 

 torial incision is made round the ovary, the style and upper part 

 of the ovary can be lifted off like a cap from the mass of ovules, 

 and the prolongation of this central swelling will be withdrawn 

 from the pollen-canal. Wanting also in the wall of the ovary are 

 the points of separation which enable us to determine the number 

 of carpellary leaves concerned in its formation ; these, however, are 

 assumed to be five, from consideration of the numerical symmetry 

 of the other floral parts, and from the circumstance that in many 

 Primulaceae the fruit-capsule dehisces at its apex with five teeth. 

 In Primula itself the number of the teeth with which the capsule 

 opens is irregular. Instead of Primula, species of Lysimachia 

 (Loose-strife, Creeping Jenny, Money-wort, etc.), or of Anayallis 

 (Scarlet Pimpernel, Bog Pimpernel, etc.), can be used with the 

 same results ; they all bear their ovules on a free central 

 placenta. 



Adherent Ovary of (Enothera. A multilocular inferior or 

 adherent ovary we will find in (Enothera biennis (evening 

 primrose), or any other (Enothera, or in Epilobium. The ovary 

 here often lies considerably below the point of insertion of the 

 floral envelopes. The cross-section shows four cells or loculi. 

 The placentae arise from the inner angles of the cells ; they 



