14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



in Plectis. The pinnae number J^ on a side and attain 115 cm. in 

 length near the middle of the leaf, compared with 63 pinnae in Plectis, 

 90 cm. long. The upper pinnae are reduced to 60 cm. in Rooscvcltia, 

 in Plectis to 37 cm. 



The leaf-sheath is indurated and somewhat bulged in the middle of 

 the lower part, extremely hard when dry, the outer surface nearly 

 smooth, finely and irregularly striate, with the lines broadly and regu- 

 larly sinuate near the base, thus affording space for the development 

 of the young inflorescence, which apparently reaches nearly full size 

 before the leaf falls. The remarkable thickening of the lowest joint 

 of the peduncle may have a function in rupturing the base of the leaf- 

 sheath at the proper time, although the sheath splits on the opposite 

 side. Inner surface of sheath a much darker brown, deeply and 

 coarsely striate when dry, also showing sinuate lines marking the 

 courses of the fibers, but more prominent on the side supporting the 

 petiole, there with 6 or 7 rows of fibers, distinctly coarser than those 

 of the thinner sections ; thickness of the middle section in the dry 

 state attaining 5 mm., elsewhere about 1 mm. thick. The thickening 

 of the sheath in the middle extends to the base, including the leaf- 

 scar ; length of leaf -scar below the thickened section usually about 

 1.5 cm., sometimes nearly 2 cm., about 1 cm. on the other side. The 

 upper part of the leaf-sheath, the back of the petiole, and the lower 

 part of the rachis with a distinct pale vitta nearly 2 cm. wide, of harder 

 tissue and somewhat more prominent than the neighboring surface. 



Petiole 4 cm. wide, deeply grooved, very densely beset with coarse 

 rusty-brown scales on the upper side, underneath with only minute 

 scattered brownish scales, the surface with rather thin, minute ap- 

 pressed tomentum, appearing silvery or glaucous. Considering the 

 petiole morphologically as a naked basal section of the rachis, the 

 length would be reduced by the pinnae extending lower down, and this 

 is indicated by the lower part of the rachis being grooved in Roosc- 

 vcltia, but nearly flat in Plectis. 



Rachis measuring 343 cm. in the only complete specimen, broadly 

 grooved at the base, nearly 4 cm. wide, narrowed gradually and thick- 

 ened in the middle, the ridge widening and the lateral margins sharp- 

 ening, soon forming a distinct lateral groove where the pinnae are 

 inserted, the groove gradually wider and deeper, with the median 

 ridge gradually narrowed and the lateral projection above the groove 

 gradually suppressed, till only a thin median flange remains, rising 

 about 1 cm. above the insertions of the pinnae. On the terminal third 

 of the rachis the median flange is suppressed gradually, and the rachis 



