134 BOTANICAL GAZETTE [FEBRUARY 
elements of the hard bast, yet as these are thinner-walled they 
tend to collapse and show an irregular outline in cross-sections. 
The expanded ends of the large rays of Juglans cinerea are 
noticeable in rather thin specimens of phloem from young trees or 
small branches, but are seen in only rather thick phloem of Juglans 
nigra. ‘The large sieve tubes of Juglans nigra and Juglans cinerea 
have long, crowded, lateral sieve plates like those shown in fig. 
3 for Carya, but the smaller sieve tubes have sieve plates that are 
farther apart and have an oval or circular outline. 
There are no crystals in the phloem of Pterocarya except druses 
in the parenchyma of root phloem. The phloem of Péerocarya 
has nearly continuous bands of bast fibers alternating with wider 
bands of sieve tubes and bast parenchyma. The lateral sieve 
plates in Pierocarya are practically the same as in Juglans, except 
that in the larger sieve tubes some of the longer sieve plates are 
divided obliquely by thin bars. The lateral sieve plates of Juglans 
and Pterocarya show equally as well developed callus as Carya 
glabra, though the sieve tubes do not appear to function as long. 
In some specimens taken from branches of Pterocarya and Juglans, 
callus was evident only on the fifth or sixth row of sieve tubes from 
the cambium. While in similar specimens of Carya, callus was 
present farther from the cambium and was on several rows of sieve 
tubes. 
Where sieve plates occur on the side of a sieve tube next the 
companion cell, unilateral callus was observed. This callus 
resembles the unilateral callus described by STRASBURGER’ 0n the 
sieve plates of sieve tubes of Abietineae next to the marginal ray 
cells. 
Lateral callus is plentiful in the sieve tubes of Castanea, Salix 
fragilis, and Populus trichocarpa, though usually not so thick as on 
the end walls. 
A sort of tyloses occurs occasionally in the older sieve tubes of 
the Juglandaceae. It is formed not by the wall of a parenchyma 
cell pushing in through a pit, as in the vessels of the xylem, but 
by a portion of the sieve tube wall subtending a parenchyma cell 
growing bodily into the sieve tube. The tyloses of the sieve tubes 
3 STRASBURGER, Ep., Histologische Beitrage 3:189r. | 
