Ewart — On the Staminal Hairs of Thesium. 281 
In T. debile the perianth-filaments are longer, being composed 
of six or eight cells set end to end, but only one cell thick. 
As before they hang from the thickened perianth-apex 
and from the lateral margins of the segments. In this species 
the stigma is farther from the top of the perianth than before, 
but the filaments almost reach it, in consequence of their 
greater length. 
This flower seems to lead naturally up to that of T. 
capituliflorum , and the five species described seem to fall 
into two converging series, thus : — 
I. Thesium spicatum and capituliflorum , with 
(a) downwardly directed thick staminal hairs, arranged 
in groups on either side of the stamens ; 
(b) long pendent perianth-filaments, several cells thick ; 
(c) short style, scarcely reaching above the base of the 
anthers, or below them ; 
(d) apex of perianth-segments much thickened. 
II. Thesium debile, panicidatum and alpinum , with 
( a ) upwardly directed staminal hairs, long and slender, 
arranged in groups behind the stamens ; 
(b) short projecting perianth-filaments, or none at all ; 
(( c ) style reaching above the base of the anthers ; 
(d) apex of perianth-segments only slightly or not at 
all thickened. 
In order to see if the other members of the genus bore 
out this classification with regard to the structure of the 
flower, I examined about forty-five other species of Thesium 
and neighbouring genera. These all fell into the series, in 
the order given below, and the following gradations were 
exhibited in passing from one to another. Starting with 
T. himalense , and passing downwards to T. scabrum (a longi- 
tudinal section of whose flower is represented in Fig. 11). 
(1) The staminal hairs become shorter and a little thicker, 
at first passing completely over the anther, and then 
barely reaching to its top. 
(2) The style, at first very long and projecting beyond 
