Observations on the germination of Phoradendron villosum and P, 
californicum 
W. A. CANNON 
A few years since, when in California, I had the opportunity of 
studying the structure and noting certain physiological peculiarities 
of Phoradendron villosum.* The study was confined almost en- 
tirely to mature forms, only a few relatively young plants were 
secured, and no seedlings were seen although I searched diligently 
for them. Neither was I successful in germinating the seeds. 
_It is with the idea of supplementing that work with some account 
of the younger stages of the life history of the mistletoe that this 
sketch is presented. 
Among other things I showed in the preceding paper that the 
spreading of the mistletoe in the host occurs in the cortex only, 
a fact well known,t} and also that this takes place because the 
haustoria are supplied with secreting cells from which probably 
exudes a solvent capable of dissolving the cell-walls of the host. 
It however was noticed that not all of the host-tissues were af- 
fected by the haustoria. For instance, their enzymes were appar- 
ently incapable of dissolving the suberized walls of the cork as 
well as the lignified grit-cells in the cortex, and this may account 
in part for the fact that the haustoria do not penetrate into the 
woody central portion of the stem. Of course in the latter instance 
other questions enter, as for instance the necessary change in 
function of the haustoria to water-absorbing organs, but as regards 
the grit-cells there can be no doubt. These were frequently noted 
lying within the tissues of the parasite and completely enclosed 
by them, which means that at an early stage in the development of 
the plant the grit-cells, like the other and adjacent cortical cells 
of the host, came into contact with the solvent secreted by the 
* The anatomy of Phoradendron villosum Nutt. Bull. Torrey Club, 28: 374. 
Igol. 
% {Kerner and Oliver. Natural history of plants, 1: 216.— Peirce. On the 
Structure of the haustoria of some phanerogamic parasites. Ann. Bot. 7: 317. 1893- 
435 
