SHOOTS. 



79 



nation and seed-distribution. 

 It is necessary to call attention 

 to certain peculiar features of 

 this type of stem. 



56. Structures. The joints 

 of the stem do not spread 

 apart, so that the peculiar 

 leaves are kept close together, 

 usually forming a rosette-like 

 cluster (see Fig. 71). These 

 leaves are of four kinds : the 

 lowest (outermost) ones (indi- 

 vidually sepals, collectively 

 calyx) mostly resemble small 

 foliage leaves ; the next higher 

 (inner) set (individually petals, 

 collectively corolla] are usually 

 the most conspicuous, delicate 

 in texture and brightly col- 

 ored ; the third set (stamens) 

 produces the pollen ; the 

 highest (innermost) set (car- 

 pels) form the pistil and pro- 

 duce the ovules, which are to 

 become seeds. These four sets 

 may not all be present in the 

 same flower ; the members of 

 the same set may be more or 

 less blended with one another, 

 forming tubes, urns, etc. (see 

 Figs. 72, 73, 74) ; or the dif- 

 ferent members may be modi- 

 fied in the greatest variety of 

 ways. 



Another peculiarity of this 

 type of stem is that when the 



FIG. 72. A group of flowers of the rose 

 family. The one at the top (Poten- 

 tittd) shows three broad sepals, 

 much smaller petals alternating 

 with them, a group of stamens, and 

 a large receptacle bearing numer- 

 ous small carpels. The central one 

 (Alckemilln) shows the tips of two 

 small sepals, three larger petals 

 united below, stamens arising from 

 the rim of the urn, and a single pe- 

 culiar pistil. The lowest flower (the 

 common apple) shows the sepals, 

 petals, stamens, and three styles, 

 all arising from the ovary part of 

 the pistil. After FOCKE. 



