* 5 2 
H. Stuart Thompson. 
1782, in a bog below Blackdown, Mendip. In 1903, also, he 
mounted a fine seedling of V. dioica with flowers of P. palustvis 
from Askham Bog, Yorks, where both plants grow. 
Jt 
Fig. 1. A. Radical leaves of Parnassia palustvis. B. Radical leaf of 
Valeriana dioica. Drawn from herbarium specimens. 
The general similarity of the radical leaves of the two plants is 
shown in Fig. 1, which also exhibits one of the leading differences, 
viz., that Parnassia has palmate and Valeriana dioica pinnate venation. 
On careful examination further differences become apparent. The 
leaves of Parnassia are more leathery and have more slender petioles 
than is the case in the marsh valerian. The radical leaves of 
Valeriana dioica are also ciliate, 1 being edged with short stiff white 
“cilia” which sometimes continue down the petiole. The veins on 
the under sides of the leaves are also densely pitted with minute 
white pores. Both the “ cilia ” and the pores are hydathodes 
encrusted with calcium carbonate. The yellowish-brown spots, 
due to tannin cells, on the lower surfaces of the leaves of Parnassia 
1 None of the British floras in common use, except Hooker’s “Student's 
Flora,” mentions the ciliation of the leaves of Valeriana dioica. 
