356 



FOURTH GROUP. — SEED-PLANTS. 



two things are fundamentally distinct. Sometimes the branching is bilateral in one 

 plane right and left of the median line, as in foliage-leaves, so that the branched 

 stamen appears to be pinnate, as in Calothamnus (Fig. 277 j/), where each pinna 

 bears an anther ; but in other cases it is in the nature of a polytomy, as in Ricinus 

 (Fig. 278), where the separate filaments emerge from the torus as simple protu- 

 berances, and each protuberance repeatedly produces new protuberances, which 

 ultimately develope by intercalary growth into a filament with many and repeated 

 ramifications bearing anthers on all their free extremities. In the Hypericineae, after 

 the formation of the corolla, from three to five large broad protuberances appear on 

 the circumference of the floral axis (Fig. 279, II-IV,d), each of which gradually 

 developes smaller roundish prominences from the apex to the base ; these are the 

 rudiments of stamens and are connected at the base in the original protuberance, 

 being branches of it. A transverse section through the flower-bud before expansion 

 shows, especially in Hypericum calydnum, the numerous filaments belonging to one 



Flo. 279. Development of the flower of Hypericum perforatuDi. I young flower-bud in the axil of its bract B with 

 two bracteoles bb; s the sepals, p first indication of petals. // middle portion of a somewhat older bud ; y rudiment of 

 the ovary, aaa the three stamens with their branches appearinjf as protuberances, ///a flower-bud of nearly the same 

 age as //, but seen from the side; s a sepal, a a the stamens, j^the ovary. /Kand ^buds in a more advanced state, the 

 letters denoting the same parts as in /, //, ///. i, 2, 3 are ovaries in various stages of development and cut through 

 transversely. 



origin closely crowded together into one bundle. In this and similar cases the 

 common primordial base of the stamen remains very short, while the branches 

 elongate considerably and appear later as a tuft of filaments springing from the torus, 

 so that their true nature could only be known from the history of development' ; if, 

 on the other hand, the primordial basal portion elongates as in Calothainnus and 

 Ricinus, the stamen in the matured condition is readily seen to be branched. 



The coherence of the stamens which stand side by side in the same whorl is not 

 less miportant for recognising the general plan of tlie structure of a flower and the 



Beitr. z. Morphol. u. I'hysiol. d. Blattes, III (Bot. Ztg. 1882). 



