MEMOIRS FROM THE DEPARTMENT OP BOTANY OF COLUMBIA UNIVERSITY 9 



somewhat the same way from the lateral portion of the axis as the integuments of the 

 seed do from the funiculus. It begins as an annular thickening some distance below the 

 apex of the axis ; this thickening enlarges in Fragarict, Comarum, Argentina, Sibbaldia 

 and several Potentillae and Ivesiae to a nearly flat disk, bearing the bractlets, sepals, 

 petals and stamens on its margin. More commonly, however, the margin curves up- 

 ward and the disk becomes cup-shaped, campanulate or turbinate (in other tribes even 

 tubular), enclosing the l-eceptacle with its pistils and often exceeding it in height. 



As the epidermal tissue of the outer or lower surface of this cvip is nearly the same in 

 structure as that of the bractlets and sepals, it has usually been regarded as a part of the 

 calyx. This view, although erroneous, is still adhered to in all our American works on 

 descriptive botany. There is no need, however, of perpetuating a faulty application of 

 the term calyx and I shall not use it in the sense given. As the term receptacidar cup (or 

 if elongated, receptacidar tube), which expresses the correct idea, is very inconvenient in 

 descriptions and almost wholly unknown to American botany,^ I shall adopt, in my 

 descriptions, for convenience, the shorter term hypanthium for the cuplike expansion of 

 the flower-axis and designate the free leaves of the outer set of floral envelopes by the 

 word sepals. 



The inner surface of the hypanthium is covered with a more or less glandular 

 tissue, which is generally thickened where the stamens are inserted. In Fragaria, 

 Potentilla, etc., the distance between the base of the receptacle and the stamens is very 

 small, while in Horkelia ( including Ivesia ) these are quite removed from each other. 



FLORAL ENVELOPES. 



The sepals are in most species normally five in number, but in a few only four ; they 

 are inserted on the outer margin of the cup, as stated above, and more or less imbri- 

 cated in the bud. Outside of the sepals and alternate with them, in all genera of the 

 tribe, except C/iamaerhodos, there is a set of similar often smaller organs, usually called 

 bractlets. They have been regarded as representing a set of bracts, also united with the 

 sepals or else a set of outer floral envelopes, an outer calyx. The view now most com- 

 monly held is that each represents two united stipules as often found in opposite or 

 whorled leaves. 



The petals are of the same number as the sepals and alternate with them. They 

 are inserted in the angle between the sepals and slightly inside the same. If the stami- 

 niferous disk is thickened their insertion is just under its margin. 



The form of the petals is variable. In Potentilla pi'oper they are most commonly 



1 So far as I know, no one in America has used the term, except myself in the Flora of Nebraska, part 21. 



