SHOOTS. 



79 



nation and seed-distribution. 

 It is necessary to call attention 

 to certain peculiar features of 

 this type of stem. 



5G. 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 greatesl 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- 

 litta) shows three broad sepals, 

 much smaller petals alternating 

 with them, a group of stamens, and 

 a large receptacle hearing numer- 

 ous small carpels. The central one 

 (Alcln milla) 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. 



