July 1000.] BOTANICAL SOCIETY OF EDINBURGH 333 



trunk tliat supplies the epicalyx segment to which each 

 petal is opposite (Fig. 12/jav.s.). 



Andnecium. — According to Payer (Traitu d'organ. 

 comp. de la lleur.) this is either isostemonous with five 

 stamens opposite the sepals (Stbhaldia), or opposite the 

 petals {Chamrrrhodos), or diplostemonous, with one wliorl 

 superposed to the sepals, and another to tlie petals 

 {Horkelia.) Further, diplostemony may arise by de- 

 duplication, ten stamens being found in a single whorl 

 in pairs, superposed either to sepals or petals. 



Dickson's studies on the stamens of the Eosacens are 

 found in " Journ. of Bot.," vols. iii. and iv., and " Trans. 

 Bot. Soc," vol. viii. In the latter he points out that 

 the androeciiim of the Potcntillas is arranged in the 

 form of a series of festoons stretching from petal to 

 petal, each festoon being concave externally. He regarded 

 the androecium as composed of five compound stamens, 

 the terminal lobe of each developed as a petal so called, 

 and the lateral lobes as fertile stamens. Where a stamen 

 is exactly superposed to a sepal, he regarded it as 

 stipular in character — an interstaminal lobe, — bearing 

 the same relation to the compound stamens on either 

 side of it as the epicalyx segment does to its adjacent 

 sepals. Dickson examined the androecia of twenty-nine 

 species, and founded three types thereon of staminal 

 arrangement. 



Type 1 had twenty stamens arranged in five festoons 

 of three each, and five single oppositipetalous stamens. 

 This is the commonest type among the Eosacea? ; it 

 occurs, for example, in Fragaria and Comarum. 



Type 2, with thirty stamens arranged in five festoons 

 of five, and five oppositipetalous stamens. This occurred 

 in three species. 



Type 3, with twenty-five stamens in five festoons of 

 five. This occurred in two species — P. fvuticosa, L. ; 

 and P. rupestris, L. 



Dickson emphasised the great importance of these 

 staminal arrangements in establishing, or at least limiting, 

 minor groups. My observations confirm the above, and 

 enable me to indorse Prof. Dickson's remarks regarding 

 the classificatory importance of the staminal arrangements. 



