42 Universifji of Calif oruut Piihlicdfidiis in Botany [Vol.7 



II. The Subterranean Organs of Trillium Species 



The stoi'agc sti'uctui'c of TviUinm consists of a stout subterranean 

 stem provided willi a iclatively large terminal ImuI, or "crown," and 

 perennial roots. In shape the rootstock of T. sessile var. (liganteum 

 is usually nearly cylindrical, but tapei-s slightly to one or both ends. 

 It varies in length from 3 to 8 cm. and in diameter from 2 to 5 cm. or 

 more. The rootstock of T. ovatum is more slender, varying in length 

 from 2 to 4 cm. and in diameter from 5 to 15 mm. (cf. Rimbach, 1902). 

 In both species the rootstock is either erect or horizontal. When the 

 rootstock is buried deeply it usually stands erect, as Rimbach {loc. cit.) 

 states for T. ovnlioii. Often, as noted by Rimbach, the rootstock of 

 T. ovatum may gi'ow sharply downward at the crown end, and thus 

 the erect terminal hud makes an acute angle with it. 



Since the rootstock in general grows only enough to make room 

 on its surface for the bases of bud sheaths and axillary structures, the 

 annual growth is slow, probably never more than two centimeters. 

 Rimbach states that the rootstock of T. ovatum does not grow more 

 than 1 mm. per year, but I have seen specimens that showed indication 

 of an annual growth of 2 mm. or more. The scars on the surface left 

 by the decay of the bases of aerial shoots furnish a good indication 

 of the amount of annual growth, but when a plant sends up several 

 shoots per year one must depend more upon the slight annual con- 

 strictions of the rootstock, which are often readily discernible. As 

 growth goes on at the "crown" end of the rootstock the base rots 

 away, generally leaving a smooth scar ; the age of tlie living portion 

 of the rootstock does not thus necessarily indicate the actual age of 

 the plant. Rimbach further states that the rootstock of T. ovatum 

 sometimes contains the living product of twenty to forty years" growth, 

 but that is far too great an estimate. Carl Purdy, the well-known 

 horticultural authority on California Liliaceac, informs me that in his 

 experience Trillium rootstocks seldom persist entire for more than 

 fifteen years even in well drained gravelly soil, and in ordinary garden 

 soil the rootstock of T. sessile var. giganteuni contains the living pro- 

 duct of less than five years' growth. It would seem that Rimbach, 

 who collected his material on the sloi)es of JMount Tamalpais, I\Iarin 

 County, must have based his conclusions as to the persistence of root- 

 stocks upon the rate at which young rootstocks grow during their first 

 four or five years. The evidence furnished by my own collections 

 made in the same locality and elsewhere confirms the statements of 



