238 , BOTANICAL GAZETTE [MARCH 
feature was the relatively small amount of phloem present. In 
Paeonia and Thalictrum, for example, there may be only 6-12 
sieve-tubes in a bundle having perhaps 30~50 times that number 
of xylem elements; but often in woody plants only a few rows of 
sieve-tubes, as seen in radial section, are really functional. 
Fics. 1-3.—Fig. 1, one-third of a sieve-tube of Juglans nigra: a, end sieve-plate 
in cross-section; 6, lateral sieve-plate in face view; fig. 2, one-half of a sieve-tube of 
Vitis labrusca: a, end sieve-plate in cross-section: 5, lateral sieve-plate in face view; 
¢, companion cell; fig. 3, full length view of a sieve-tube of Lactuca scariola: a, end 
sieve-plate in cross-section, with callus; b, slime contents; c, companion cell; d, lattice 
or ‘“‘sieve-field.” 
No lignification of the phloem was observed in Helianthus. 
Perhaps the material used was collected too early or grew under 
different conditions from that described by BoopLE.5 
’ Boonie, L. A., Lignification of phloem. Ann. Botany 16:180. 1906; also 
ibid. 20: 319-321. 1910. 
