24 



ON THE FERTILIZATION 



ded, the otl 



oval or rod like (Plate IV, ftg. 7). The pollen does not 



two nuclei-one ro ^^ ^ dehiscence if the stamens are undisturbed by insects. 

 tendtue^I* the period of access of insects and that of maturation is 



' *:JZ m Z a datively late period is almost limited to the axes of the flowers. 

 v'7 *7nn of the axis takes place both beneath the origin of the outer perianth, so that 

 he Iter ceases to be sessile, and above it, causing the closed inner perianth to force the 

 ilZoi the outer one apart and appear prominently beyond them, and forcing the summit 

 of 'he terminal portion of the axis with the stamens more and more against the cupola of 

 the inner perianth. The flower at the same time emerges from within the sheathing bract 

 and projects beyond it. The filaments for long remain almost unaltered in length while 



F within the anthers. This is, no doubt, related to the reten- 



tioTof the stamens within the closed inner perianth, and the consequent protection of the 



from maceration in the receptacular fluid. There is comparatively little increase in 



nittturative chan 



cr 



o 



the 1 8 



size 



i the anthow for some time, but the evolution of the pollen goes on, tetrads be 



nh ed by distinct small grains of normal form. These are at first uninucleate, and measure 

 al ut 99 X G'6/i. in diameter. Distinct grains of such character are present within the anthers 

 at a time wlion the lobes of the outer perianth have only begun to separate and the filaments 

 ihow no appreciable elongation. As maturation approaches, and just before the absorption 

 of the receptacular fluid, the anthers become visibly swollen and the filaments begin to grow 



rapidly. As the stamens are still enclosed within the closed cavity of the inner perianth, the 



filaments are not free to grow directly onwards or outwards, but become extremely 



gating 



folded upon themselves, the basal portion running downwards along the sides of the axis, and 



the distal halves being folded upwards more or less parallel to them (Plate IV, fig. 1 



•> 



The inner perianth becomes more and more stretched by the increasing bulk of the 

 stamens and the upward growth of the terminal portion of the axis from which they arise, 

 and the tensioi ultimately becomes so great that rupture occurs. As a rule, this occurs at 

 the summit, so that the inner perianth comes to form a cup or funnel around the upper part 

 of the flower ; but in some instances it takes place at the base, and the perianth is then carried 

 upwards as a cap on the apex of the axis and the stamens until the latter expand and lacerate 

 it. liupture of the inner perianth does not usually occur until the absorption of the recep- 

 tacular fluid has taken place, but in exceptional cases it may partially occur before the 

 fluid has entirely disappeared. Once rupture has taken place, the complete evolution of the 

 flower occurs with great rapidity. The stamens become widely divergent and protrude 

 far beyond the ruptured perianth (Plate II, fig. 1, b). The extreme protrusion is due partly 

 to the tip of the axis rising on the removal of the restraining pressure of the perianth, and 

 partly to continued growth in the stamens, but to a much greater extent to mere unfolding 

 of the filaments. The divergence of the stamens varies in degree in different instances, and is 

 specially marked in flowers in which abortive female organs are present. Dehiscence next 

 sets in in the faces of the lobes of the oval anthers, but, as previously mentioned, spon- 

 taneous discharge of pollen does not seem to occur. 





C— Characters of male flowers in mature gall-receptacles to which insects have 



not gained access. 



In many cases little or no farther growth seems to take place after the time at which the 

 receptacle was ready for the access of insects, and the flowers merely undergo a gradual 

 process of desiccation. In some, however, as has been already mentioned in describing 



