12 MEMOIRS FROM THE DEPARTMENT OF BOTANY OF COLUMBIA UNIVERSITY 
stamens, as, generally in Potentilla pentandra, Horkelia Gordonii, H. Shockleyi, H. Bailey, 
H. lycopodioides, Comarella multifoliolata (Fig. 12), ©. sabulosa and Sibbaldia procumbens. 
Chamaerhodos is an exception to the rule (Fig. 11) in which the androecium consists of 
the 5 antipetalous stamens. Stellariopsis santolinoides (Fig. 19) has always only 15 
stamens and Potentilla Monspeliensis sometimes that number. In both the antipetalous 
stamens are then lacking. In the former species they are represented by a thickening of 
the tissue at the base of the parapetalous stamens. 
There is, however, within the tribe Potentilleae also another arrangement of stamens 
widely different from the one described above. (See Figs. 1 and 13.) My attention was 
called to it especially in 1896 while studying a new species, P. convallaria, nearly re- 
related to P. arguta and P. glandulosa. Tt may be described as follows: ‘The margin of 
the disk is very thick; this collar-like rim (Fig. 1) is pentagonal in outline, with one 
petal (p) fastened at each corner ; in cross-section the collar is nearly semicircular and 
bears on its upper surface 20 to 30 stamens ; these are not arranged in definite series, 
but form concave arches (Fig. 13, fs) between the bases of the petals; the number of sta- 
mens in each is very variable, being 4, 5 or 6 in each arch in the same species or even 
in the same flower. The stamens on each side of the bases of the petals are the oldest, 
then the ones next to them, ete. Those opposite the sepals (as, Fig. 13) are, therefore, 
the youngest, a condition entirely contrary to that found in the other Potentilleae. It 
was this peculiar structure, although not well described by him, that led Bigelow to 
make Potentilla arguta the type of a new genus, Bootia. One of our recent botanists, in 
a paper published a few years since, slightly ridiculed Bigelow for so doing, saying : 
“What a genus!” It must be admitted that the above mentioned peculiarity alone 
would searcely warrant the exclusion of the species in question from Potentilla. There 
are, however, other characters, more important, which I shall discuss later, that in my 
opinion fully warrant such an exclusion. 
Alexander Dickson’ gives an interesting discussion of a similar arrangement of the 
stamens in P. fruticosa, in which the festoons generally contain 5 stamens ; he explains 
the arrangement in the following words: “ As Lam unable to conceive of any possible 
explanation of such a festooned arrangement of stamens, unless we view the androecium 
here as consisting of five compound and confluent stamens, the terminal lobe of each 
such stamen being developed as a petal, so-called. When there are five stamens in the 
festoon, the central stamen must be regarded as an interstaminate lobe, analogous to the 
interpetiolar stipules—to the intersepaline lobes in some species of Campanula, in Nemo- 
phila, and in Potentilla itself (the so-called epicalyx ), or the interpetaline lobe of the 
corolla of Soldanella.” 
1Seemann, Journ. Bot. 4: 273-281. 
