Thalictrum Ranunculaceae 473 



but is infrequent south of it. It is usually found in springy and rarely 

 in drier situations. 



I am following Fernald in considering this a variety of Ranunculus 

 septentrionalis although it seems distinct in characters other than its 

 pubescence. The whole plant is much more robust than its allies, has 

 much larger fruiting heads, longer styles, and the achenes usually average 

 40-50 per head while the species usually has about 20. I have had the 

 last two species and this variety under cultivation for years. While this 

 treatment was being written during the last of June I visited my colony 

 of this variety and I found plants 5 feet in diameter with an abundance 

 of new plants coming from the nodes. Usually the new plants have 3-5 

 radical leaves 5-8 inches long and the pubescence on the petioles of all of 

 the leaves from one node is spreading, but sometimes at other nodes some 

 petioles have a spreading pubescence and some have a recurved pubescence 

 toward the base. The main stem above the first node has a sparse spread- 

 ing pubescence. The plant seems to have the retrorse hereditary factor 

 of the pubescence but a quantitative statement is speculative. 



Ohio and Ind. to Minn., southw. to Mo. 



2548. THALICTRUM [Tourn.] L. Meadowrue 



Stem leaves all petioled; flowering in April and early May, dioecious; plants gen- 

 erally less than 6 (8) dm high 1. T. dioicum. 



Stem leaves sessile or only the lower ones petioled; generally flowering after May, 

 dioecious or polygamous; plants generally 8-20 dm high. 

 Lower surface of leaflets, especially the veins, and usually the achenes, covered more 

 or less with stalked or sessile glands, or with both; leaflets generally thick and 



with revolute margins; plants generally with yellow roots 2. T. revolutum. 



Lower surface of leaflets without glands but more or less densely pubescent with 



flat, multicellular hairs, very rarely a specimen glabrous. 



Leaflets thick tfr thin, the margins more or less revolute; flowering mostly in 



June; anthers mucronate, or at least somewhat acute, generally about 2 mm 



long; filaments usually more or less enlarged above; mature achenes sessile or 



nearly so, not reflexed 3. T. dasycarpum. 



Leaflets thin, the margins flat; flowering mostly in July; anthers mostly 0.5-1 mm 

 long, oblong, obtuse at the apex; filaments usually flat and much enlarged 

 above, usually about as wide as the anther; mature achenes stipitate, re- 

 flexed. 4. T. p&relegans. 



The treatment of the genus as given is not at all satisfactory and must 

 be regarded as provisional. Until the many species described by E. L. 

 Greene are understood, no satisfactory treatment is possible. I believe 

 the "master key" to our species has not yet been discovered. The char- 

 acters usually given to separate the species are not constant in a large 

 series of specimens. What effect the habitat has upon the thickness of 

 the leaflets I do not know but I do not think we should place thick- and 

 thin-leaved specimens in the same category. 



1. Thalictrum dioicum L. Early Meadowrue. Map 975. Generally 

 frequent throughout the state on wooded slopes. This species, like the 

 others, shows considerable variation but I believe we do not have any 

 of the described varieties or closely allied species. 



