144 
POPULAR SCIENCE REVIEW. 
lias of shortening the term of life of the plant. Other cases of 
natural union are worthy of remark, especially the union that 
sometimes takes place in roots. For many years it has been 
known that the stumps of silver-firs increased in diameter after 
the trunks had been felled. Here was a pretty case for those 
who held the presence of leaves as an essential to the due 
formation of wood. How would they get over this difficulty — 
that wood there was, and yearly increasing, and yet no leaves ? 
Even quite recently one of our agricultural societies has awarded 
its prize to an essay in which the phenomenon in question is in 
some way or another explained by the antiseptic action of 
peat ! What a delightful discovery ! Would that the salt-beef 
in the brine-tub would increase in like manner! Jesting 
apart, the cause of the annual growth of the stumps of the 
silver-fir was satisfactorily shown some twenty years ago by the 
Herman botanist Groeppert.* He was enabled to prove that 
the roots of the felled tree inoculated with those of adjacent 
trees, and that a communication of the nutrient fluids from the 
sound tree served to keep life in the maimed one. Doubtless 
a similar root-union exists in other cases, and affords the 
explanation of the formation of those seemingly detached 
knobs of oak that one occasionally meets with. 
Another instance of root-union is worth mention, not only 
for its inherent singularity, but because it will yield us im- 
portant evidence by and by. We allude to the case of the red 
■and white carrot recorded by Lindley. The two roots by some 
means became twisted one around the other and firmly united 
together. But this was not all. While the tops or crowns of 
the two carrots preserved their natural appearance above the 
point of union, it was very different below. In fact the cha- 
racteristics of the roots below the union were exactly transposed. 
What should have been a red root became white, while the white 
root blushed with a redness not its own. We may illustrate 
what happened in the case of these carrots by the letter X, con- 
sisting as it does of two lines, one thick the other thin, crossing 
in the centre. Now, suppose the thick line to become thin 
below the junction, and the thin line to become thick, and we 
shall have a change analogous to that which took place in the 
carrots aforesaid. 
Another curious phenomenon occasionally met with is the 
union of embryo to embryo, either within the seed or imme- 
diately after germination. In most cases a seed contains but 
one embryo plant, but there is always a provision made for 
more than one, and in fact sometimes two or more are produced, 
as in the orange (Citrus). The mistletoe is one of these 
* “ Ann. Sc. Naturelles,” xix. 1843, p. 181, t. iv. 
