1886.] 



295 



[Trelease. 



tical, oblong or linear, pointless, mucronate or with a (usually thin 

 and flat) cuspidate prolongation of the connective ; and the char- 

 acter of the achenia, which are sub-sessile or stipitate, papery or 

 thick-walled, terete, somewhat two-edged or compressed, grooved, 

 ribbed or with free or anastomosing veins, and either nearly point- 

 less or prolonged into a beak, bearing the remains of the stigma. 



The foliage is not readily described so as to be of value, and is 

 subject to considerable variation in most species, but it is some- 

 times characteristic to the eye, as the texture and surface of the 

 leaflets and the form and disposition of their lobes yield good 

 characters. The form and margin of the dilated base of the peti- 

 ole, which in some cases is more or less free and stipuloicl, and the 

 presence or absence of stipels to the leaflets cannot, apparently, 

 be depended on for the discrimination of species. 



The plants are usually glabrous or glaucous, but vary a great 

 deal in this respect. When not pubescent, the lower surface of 

 the leaflets not infrequently appears finely granular under a lens, 



©DP 3 



Fig. 2. Trichomes of Thalictrum. 

 1. T. Fendleri, var. Wriglitii. 2-3. T. purpurascens, 



magnified. 



from the prolongation of the apices of the epidermal cells into 

 blunt, thick-walled papillae (fig. 2, 1). With these granulations, 

 are associated, in several species, straight, cylindrical hairs (flat- 

 tened and ribbon-like only when dry), consisting of a single row of 

 elongated cells (fig. 2, 2). These are most abundant on the lower 

 surface of the leaflets, on the pedicels, achenia, etc., and, especially, 

 at the base and forks of the petioles. In other cases the same 

 parts are more or less densely covered by unicellular, glandular 

 hairs (fig. 2, 3), with or without interspersed papillae. These two 



