HISTOLOGY OF PHLOEM IN WOODY ANGIOSPERMS 349 
This type is shown in text-figure i, representing the sieve tube of 
Juglans nigra. 
"The second type is Hke the first except that the lateral sieve 
plates are less well developed and the end walls less oblique, having 
two to ten sieve plates each. This type may be shown by Vitis " 
(text-fig. 2). The sieve plates are shown covered with callus. 
Text-figs. 1-3. Sieve tube segments are shown cut longitudinally in the 
tangential plane so that the sieve plates on the end walls are seen in section and 
those on the side walls are seen face view. (See text.) 
The third type has the end wall made up of a single sieve plate 
which is placed nearly at right angles to the side walls. The sieve 
