POLUNATTON 



4r 



active participntors in the operntions 

 abovL' recorded. Tlnlr operations in pro- 

 moting crosa-polHnntion in the Cincbuua 

 prniip have been Inrpoly responsiMe for 

 iome of the most far-reachiup economic 

 conditionfl nnd results in the history of 

 the drug trade* In eiceptionni instances 

 itill other animals take part la this work. 



It mnj be remnrkf^r! in pn.sfJinjL' thai 

 theae characters, like somo of those whidi 

 follow, are not restricted to the flower it- 

 •elf. Very frequently othor portions of 

 the plant adjucent to the flower will be ex- 

 panded, brightly colored aud developed 

 iDtoax>ecia] forms, while the odor of some 

 flowers, due to the presence of glandular 



tisanes, is shared by the foliage and other 

 herbaceous portions, as in the lavender. 

 Well formed, lari^e glands are present in 



the axils of the primnry veins of the lea, os 

 of some *^pecie8 of Cinchona, although the 

 precL^ function which they perform is by 

 no njeans clenrly established. 



The special contrivances for \itilizing in- 

 > t-visit« in efTeetinx pollination are far 

 more elaboratn nnd varied than those for 

 iuduciujif them, which wc have alre.idy 

 <'MnNi(h'rrd, tiit'l onr conslder.Ttjon of tln^m 

 cannot be extemU'^l beyond what is nee-^s- 



•ary 1o itnlieat*^ their K<'neral nature rnd 



cla»M oration, and to serve as a k y in un- 

 derataiidinjj the complicated moihhcationa 

 whieli we hnve<»bwerre<| fhe typieal flower 



to nnder^ro. r^»nany the effects extend in 

 twu dirretions: <h» toward exeludin*: the 



pollen from accesis to the stigma of its 

 own flower, and (b) toward securlnj; its 

 access to that of another. One of the 

 mn«t frequent methods of securing the 

 former result is the maturing of the .in- 

 drueciuni and gynaeeium at diifereat 

 times. This method is called Dichogamy, 

 By it the ovules of a flower are already 



fertiliz T before the mature pollen of that 

 flower eseai)es from its thecae il'rotero- 

 gyny), or else the pollen is matured and' 

 utilized before the stigmas of that flower 



are prepared for its reception (Proteran- 

 dry, Figs. 232 and 233). Dichogamy is- 

 very common among perfect anemophilous 

 flowers, where self-pollination would oth- 

 erwise commonly result, and it may be as- 

 sumed to have been the first step towardi 

 the uni-sexual state, so common among: 

 flowers of that class. Careful notice 

 should be taken of the fact that in dichog- 

 amy the retarded state observed in an- 

 droeeinm or gynaeeium is but temporary^ 

 and that the finally developed forms of 

 both the iiroterandrous and proterogynons 

 flowers are practically the same. 



A far more profound niodirualion is that 

 in whii'h tln»re is a permanent change ii> 



the amlioecium (Fig. 2.'?4) of one flower 

 and a simUnr cliaiige in the gynjieeitnii 



(Flf:, -*!•'►) of another, by wl)i<h a sinnlar 

 result is obtained to that j)roc<*eiling from 

 diehognmy. Su<*h a provision eonstitutei* 

 Dimorphism. By a modlficatiou of it a 

 third form of flower, intermediate he- 

 twe<*n the other two, is itntdaced, consti- 

 tuting Trim<»rphism. As will be s*' -a by a 

 consideration of the following typieal ex- 

 amples of each* dimorphism is more inti- 

 mately eonnecteil with the tran.sferrnig I'f 

 the pollen than is dichogamy, though the 

 latter is riirely without some spi'cial pro- 

 vision for thus pupplementiug the effect 

 which it produces in excluding the pollen 

 from the stigma of its own flower. 



Fig. 2n<i illustrates a flower of v'er- 

 nonia. Jts anthers are clu.sely syn;;' ne- 

 siou^ led introrsely ilehiscent. Its style is- 

 two-<*left, the stigmas existing upon the 

 inner faces of the branches. It is obviou* 

 that until these branches separate pollin.r 

 tion eann^'^ tnke plaee. Before h sepa- 

 r.'iticn uvrur» the tip ot ihe style is, by 

 elongatiftn, slowly forced up thrnu;;h the 

 tube of the anlhrrs. The latter, with the 



contained pollen, are mature, and the p"i- 



