On Dodder. 
257 
investigatln": the growth of all the phaenogamous parasitic plants 
— of the mistletoe on the oak or apple, as well as the dodder on 
clover. 
In penetrating the stem the tissues of the attacked plant are 
not injured ; they are only pushed aside by the advancing cone, 
and the cells of the parasite are placed in such close relationship 
to those of the supporting plant that the organised juices pass 
freely from the one to the other, entering the dodder just as 
they would pass into a branch of the plant itself. The relation 
of parasitic fungi to the plants on which they grow is very 
diflerent from what occurs in the dodders and the other higher 
parasites. The small roots, or mycelium of the fungi, penetrate 
the walls of the cells, and live upon the tissues themselves, or 
on the starch or other contents of the cells. The result is, con- 
sequently, the disorganisation and destruction of the plants 
attacked by the fungus. The higher parasites, on the other 
hand, only withdraw the organised juices, l^his operation is 
without any real injury to the supporting plant, if the proportion 
of the juice withdrawn by the parasite is small in relation to 
what exists in the whole plant, as is generally the case with the 
mistletoe on the apple : or it is fatal to the supporting plant, as 
in the case of the dodder on trefoil, where the rapid growth of a 
large parasite withdraws all the prepared food, and kills the 
plant by exhaustion. The enormous mass of the dodder also 
destroys the clover which it covers, by smothering it in the same 
way that any other heavy and dense covering would. 
Of the many remarkable problems suggested by the study of 
the dodders none is more strange than the physiological inquiry 
as to how, without any appliances for obtaining food from the 
air or the soil, and entirely dependent on the prepared juices of 
the plants on which they live, they nevertheless contain in their 
tissues starch, resin, and different acrid substances which are not 
found in the nourishing plants, and, on the other hand, they 
want some of the chemical elements which abound in these 
plants. And, still further, how a single plant of dodder collecting 
its food from plants so different as clover, heather, thyme, and 
grass can convert the diverse juices of these various plants into 
products which are completely unlike any found in each or all 
of them.* 
* Tlie late Dr. Wolwitscli, tlie illustrious explorer of "Western Tropical Africa, 
in a short paper '• On the Loranthaor aj of Angola," a gioup of plants including 
onr well-known mistletoe, refers to his own experiences of these parasites as follows : 
" It seems tliat tlie qualify of the sap or juice of a tree exercises little or no 
influence upon the vegetation of Loranfhaceai ; for in several instances I found 
one of the same species growing, equally vigorously, on Adansonia, which has 
a watery juice, and at another time on fig-trees, of which the sap is milky and 
glutinous."— /oKHiaZ Boyal Hort. Soc, vol. iii. (1873) p. 12-2. 
