NOTES. 
NOTES ON THE HISTOLOGY OF THE SIEVE-TUBES OF 
CERTAIN ANGIOSPERMS.— In continuation of the researches on 
the sieve-tubes of Gymnosperms, which were published in the Annals 
of Botany, vol. xv, No. lx, December, 1901, the sieve-tubes of certain 
Angiosperms have been examined in detail by methods similar to 
those previously employed. 
The sieve-tubes of Vitis vinifera , Wistaria chinensis, Cucurbiia 
maxmia , Tilia europaea , and Viscum album have been studied with 
special reference to their ‘ connecting threads ’ and means of inter- 
communication, and they have been found to agree in their general 
characteristics and essential structure with the sieve-tubes of the several 
species of Pinus already described. 
In the mature sieve-tubes of these five plants, the end walls or 
sieve-plates are traversed by relatively large slime-strings, and each 
slime-string is enclosed in a callus-rod. In the radial and tangential 
walls slime-strings occur in groups in large or small shallow pits, 
and, except in the case of Viscum album , each of these groups, 
composed of some three to six fine slime-strings, is contained in a 
callus-rod. Such a group seen in surface view constitutes a ‘ sieve- 
field.’ The structure of these lateral sieves and sieve-fields is similar 
to that of the sieve-plates of Pinus sylvestris , &c. A median dot is 
usually visible on each thread. 
In Viscum album the lateral walls between two sieve-tubes are 
crowded with groups of fine threads in small shallow pits, but no 
callus-reaction is given by the cell-wall in their neighbourhood. 
Callus, however, does occur in the end-wall sieve-plates in connexion 
with the slime-strings. With the approach of winter, the callus-rods 
increase in size at their free ends, which unite to form callus-pads 
on both the end and side walls. The slime-strings perforate these 
callus-masses so as to unite the contents of adjacent sieve-tubes. 
[Annals of Botany, Vol. XVII. No. LXV. January, 1903.] 
