Germination of Arceuthobium occidental. ioi 
damper than elsewhere, and dampest of all in the thickets where the pines 
were small and close together. It is precisely in these thickets and close 
stands of young pines that Arceuthobium is most abundant. On some of 
these young trees, fifteen to twenty feet high, I counted over twenty 
separate bunches of Arceuthobium . On trees farther apart, or isolated, 
Arceuthobium occurs in far less numbers, if it is to be found at all. Some 
young trees in the thickets were dead, from no other apparent cause than 
the great number of Arceuthobium plants which they had borne. In many 
cases where a branch bore a particularly large and vigorous bunch of Arceu- 
thobium the branch was dead beyond the parasite, as Cannon (1901) 
observed on oaks attacked by Phoradendron. 
In the damp air of the thickets little water is lost by evaporation from 
the fruits ; if rain falls, still less. The fruits seemed to me plumper and 
more translucent than the few which I had found in the Stanford Arbo- 
retum. Without any apparent disturbance the fruits would explode ; I could 
hear them, I might even be struck by the flying ‘ seeds ’ ; but if the wind 
gently shook a bunch of fruiting Arceuthobium , or the raindrops fell upon 
the fruits, or I lightly struck a branch of pine on which the fruiting parasite 
grew, there would be a momentary fusilade, the ‘seeds’ flying in all 
directions, and sticking to whatever they struck, provided always the speed 
at the time they struck were low enough to be offset by the adhesion of 
their gelatinous outer-coats to the object struck. That the speed with 
which the ‘ seeds 5 leave the parent plant is high any one knows who has 
been struck by the hard, pointed little bodies. The speed must be great 
to carry the ‘seeds’ far, for they are heavy. It is impossible to deter- 
mine the distance to which a ‘seed’ may be thrown. I can only estimate 
this from experiments. The longest distance to which a ‘ seed ’ was thrown 
in the laboratory was fifteen feet. The air of the laboratory was dry, but 
I had kept the material, sent from Pacific Grove, in an air-tight preserve- 
jar in which there was a little water. In other words, the air surrounding 
the material was as moist as that at Pacific Grove, and the fruits were as 
plump and tense. I have no doubt, from the relative positions of my work- 
table and of the book-shelf on which the f seed ’ stuck, that it could have 
gone at least ten feet further. 
Let us turn now to the structure and mechanics of the fruit. In 
Fig. 1, Plate III, we see a small fruiting branch, natural size, which was 
growing a few years ago in the Stanford Arboretum. At Pacific Grove the 
fruits may be as many again on a branch. The fruits are complex. Morpho- 
logically they include the receptacle adherent to the ovary (Engler and 
Prantl). Skrobischewsky (1890) — only reviews of whose paper I have been 
able to see — describes the fruit of A. Oxycedri as consisting of (1) a one or 
two-layered epidermis, (2) underlying this four or five layers of collen- 
chyma, (3) parenchyma with vascular bundles embedded in it, (4) the gela- 
