316 Peirce. — On the Structure of the Haustoria 
sieve-tubes in the haustoria. This is now shown to be the 
case. Through the haustoria these parasites are supplied 
with all the food-substances which they need. 
It may be asked if all parasitic Phanerogams possess both 
sieve-tubes and tracheids or tracheae in their haustoria. It is 
evident from the structure of the haustoria of the species of 
Cuscuta studied, that these plants can absorb, not only those 
substances which are conducted through the xylem-elements 
of their hosts, but also those conveyed by phloem-elements. 
We know that, at times at least, especially in spring, the 
reserve food-materials of our perennials, converted into their 
soluble forms in the places where they are stored, are con- 
veyed through the ducts to the points where they are needed. 
At these times, the ducts contain sugars and other organic 
substances, besides water and the crude substances absorbed 
by the roots. It might have been supposed that, owing to 
the attachment of haustoria, the host of a Cuscuta was forced 
to use its stored food at once, after converting it into soluble 
form and conveying it through the ducts to the places of 
consumption, and that the Cuscuta drew away, through the 
tracheids which were long ago found in its haustoria, only, or 
little more than, these reserve matters. The presence of 
sieve-tubes in the haustoria, and their direct union with the 
sieve-tubes of the host, prove that the parasite can and does 
abstract the recently elaborated food substances in its host, 
as well as the reserve matters. 
We can now put the question in a more definite form. 
Do all phanerogamic parasites possess the appliances for 
abstracting from their hosts both reserve food-substances and 
also those freshly formed ; or are some forced, by the absence 
of haustorial sieve-tubes which unite with the sieve-tubes of 
their hosts, to depend on reserve matters only ? In order to 
be able to answer this query in part at least, I have examined 
the haustoria of Viscum album , L., two members of the 
Rafflesiaceae, Brugmansia Zippelii , Bl. and Rafflesia Patma y 
Bl., and also Balanophora elongata y Bl. 
The material of Viscum album , preserved in strong alcohol, 
