ANGIOSPERMS. 



357 



real relations of number and position in its parts. In Cucurbita, 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 ; each 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 length than the filaments form vermiform con- 

 volutions (Fig. 280, ///). 



FIG. 280. Cucurbita. Pepo. Development of the androecium ; in the three figures the simple stamen is to the right, 

 one double stamen formed by coherence of two simple ones is behind, and one to the left The anthers grow vigorously 

 in length and form convolutions. After Payer. 



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 



gynaeceum ; outside this __ 4 &>%> $ii\&$&.^ B 



tube are five vertical double 

 rows of long filaments 

 (Fig. 281 B, /) parallel 

 to each other, each of 

 which divides into two 

 arms (/) each carrying a 

 half anther. The history 

 of development and com- 

 parison with allied forms 

 shows that the tube is 

 formed by the lateral 

 cohesion of five stamens, 



u. f +V. /->/-iV> or- 'nrr movrri-no FIG. 281. Althaea rosta. A transverse section through the young androecium. 



ing margin. B a piece of the tube of a fully f ormed androecium with a few stamens, h cavity of the tube, 



-rr1i-i^A rlnnhlA rnwo r\F Vsubstanceof the tube, a the anthers, t the point where the filament divides,/ the point 



U1 where two filaments spring from the tube. A is much more highly magnified than B. 



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 1 . In Tilia, where the five primordial stamens 



* 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 



