ANGIOSPERMS. 



357 



real relations of number and position in its parts. In Cucnrbita, for example, there 

 are the rudiments of five stamens, while at a later period only three are found, but 

 two of these are broader than the third ; ea( h of the two is formed by the lateral 

 cohesion of two stamens ; the filaments unite to form a central column, on which the 

 pollen-sacs growing more rapidly in len<i;th than the filaments form vermiform con- 

 volutions (Fig. 380, ///), 



jfio I. utiiibih! /'epo. Developinei 

 • dnuhle stamen formed by coherence oft 

 en^tli and form con\nlutions. After Pay£ 



: of tlic aniiroecium ; in the three fitrnres the simple stamen is to the right, 

 •o simple ones is behind, and one t" the left. The anthers ^row vigorously 



The conditions are more complicated and more difficult to understand when 

 cohesion and branching of the stamens occur simultaneously, as in the Malvaceae, 

 In Althaea rosea, for example, the androecium forms a closed membranous tube com- 

 pletely surrounding the 



g\ naeceum ; outside this 4 



tube are five vertical double /^)C\ '/IS^'^ 



rows of long filaments J C) :^ V^ r 



(Fig. 281 B, f) parallel 

 to each other, each of 

 which divides into two 

 arms (/) each carrying a 

 half anther. The history 

 of development antl com- 

 parison with allied forms 

 shows that the tube is 

 formed by the lateral 

 cohesion of five stamens, 

 but the cohering margins 

 produce double rows of 

 lateral branches, which 



are the filaments, and each of these divides into two arms. The transverse section of 

 the young tube in Fig. 281 A shows these double rows of divided filaments quite 

 clearly ; the part (V) which lies between two of them must be considered to be the 

 body of a stamen, the margins of which right and left bear each a single row of 

 filaments as laciniae or branches ^ In Tilia, where the five primordial stamens 



Fig. 2S1. AUivJ 



A transverse section through the young androecium 

 a piece of the tube of a fully formed androecium with a few stamens, h cavity of the tul>e, 

 substance of the tube, a the anthers, t the point where the filament divides, /"the point 

 here two filaments spring from the tube. ,-/ is much more highly magnified than />. 



' This view of the matter will cease to seem strange if we consider the nature of an unilocular 

 ovary, in which the margins of the cohering carpels form parietal projections, and the ovules arise in 



