3 1 S Peirce. — -On the Structure of the Haustoria 
to be found. The haustorial cells near the phloem of the 
host are strong and thick-walled, and they abut against com- 
pressed, often dead, cells. The strand of tracheids, although 
these unite directly with the xylem-elements of the host, 
is not connected with the fibro-vascular bundles of the mother 
plant. The cambial ring of the host, severed by the young 
intruding haustorium, is joined again through the formation 
of a cambium in the haustorium. This cambium, the one 
new structure above referred to, cuts the strand of tracheids. 
Across this stratum of cambium, consisting of from two to 
several layers of cells with no intercellular spaces between 
them, the liquids drawn from the wood of the host, and con- 
ducted for a short distance by the haustorial tracheids, must 
be transferred. On the side of the cambium toward the 
periphery of the stem, the tracheids are by no means as 
regularly arranged as on the inner side, and the body of the 
borer may be massively developed, while as yet no vessels have 
been fully formed at its point of origin in the cortical root \ 
We thus see that in the haustorium of Viscum albitm 
provision is made for the conduction into the parasite of those 
substances in the xylem only of the host, and that this 
conducting system is by no means mechanically perfect. 
Being incomplete in structure, its physiological efficiency 
must also be imperfect. 
The alcohol-material of Brtigmansia Zippelii , Rafflesia 
Patma, and Balanophora elongata , very generously put at my 
disposal by Professor A. F. W. Schimper, was collected by 
him in Java in 1890, and was in excellent condition. Every 
stage in the development of these plants was represented, 
except the seeds, either ripe or germinating. 
For the question in hand, it was necessary to examine 
sections of tolerably advanced stages only, in order to 
determine the presence or absence of sieve-tubes ; but for the 
sake of completeness, I have repeated some of the work of 
earlier writers, and have studied other stages. 
1 De Bary, Comp. Anat. of Phanerogams and Ferns, p. 384. Clarendon Press, 
1884. 
