17g THE- : BOTANICAL MAGAZINE. [Vol. xxix. No. -346. 



material collected near Satporo during 1907-1909 'and has 

 therefore been able to overcome certain difficulties in connection 

 with the elucidation of the floral mechanism. His study of the 

 genus has also been greatly facilitated by an examination of 

 ample material of dried specimens of A. triphylla preserved in 

 the herbaria of Kew, the British Museum und Edinburgh. 



In the following pages a full description of the genus followed 

 by a discussion of the morphological nature of certain organs 

 and of the systematic position of the genus is given. Since both 

 the North American and the Japanese species are very similar, 

 they will be considered collectively except for certain points of 

 specific difference. 



The Leaf. 



One leaf is produced to a flower-bearing shoot in each season 

 from the terminal bud of a sympodial rhizome. Ths leaf is 

 provided with a long, slender petiole which stands upright from 

 the ground, and in a luxuriant specimen of A. triphylla measures 

 as much as 52 cm. in length. As a rule the lamina consists of 

 three sessile leaflets, but in ".abnormal specimens two or four 

 leaflcts may occur. In a small specimen it measures only a few 

 cm. in diameter, but in a very luxuriant specimen of A. triphylla 

 a diameter of 30 cm. is reached". 



The terminal leaflet is rhomboid-obovate to broadly rhom- 

 boid-obovate and is shallowly trilobed at the apex (text-figs. 

 II, 2, 5, III, 1-5). In well-devoloped specimens of A. triphylla 

 each of the three lobes again produces one or two lobes, resulting 

 in the formation of five to nine larger or smaller triangular lobes 

 (text-fig. I). In A. japonica, on the other hand, the sini become 

 much deeper, thereb} 7 producing three oblong segments, the cen-. 

 tral one of which may again be trilobed (text-fig. II, 1, 3, 4) 2 \ 



The lateral leaflets are very broadly cuneate and inequi- 

 lateral. The outer margin is unequally sinuate-dentate or irre- 



1) In A. japonica the diameter of the lamina never exceeds 20 cm. 



2) In rare cases the terminal leaflet may become quadrilobed, but not more, as 

 in A. triphylla. 



