18 



in the process of growth, made the seeds palatable to the ants ? Another experi- 

 ment also disclosed another enemy to the seeds, in a mould, which attacked those 

 deposited on a bottle surrounded by a spiral band of wool for the purpose of 

 keeping the seeds moist. 



From the numerous experiments of Du Hamel, Richard, Dutrochet, and 

 others, it would appear that the deposit of the seed on liriny matter is a necessary 

 condition of continued growth. 



The growth of the Mistletoe plant on the tree now claims our attention. 

 The usual position of the plant on the under surface of the branch has been 

 accounted for by saying that the birds, in the act of cleaning their bills, manage 

 to get the seed on the lower suiface. An hour's watching will easily correct this. 

 Missel-thrushes, song-thrushes, fieldfares, and blackbirds when feeding on the 

 seeds swallow them whole, just as they do yew or holly berries. The seeds, 

 deprived of their viscous matter, which is for the most part digested, are ejected 

 ordinarily in masses of from eight to twelve, Such masses generally fall on the 

 upper surface of the branch, and the rain mechanically carries the glutinous seeds 

 to the under surface, where they ultimately establish themselves, the viscous 

 matter still about them being sufficient to make them adhere firmly to the hark. 

 The progress from the upper to the lower surface is often slow. In this case 

 the processes are swelling during the interval, and in several instances under 

 observation the seed reached the under surface in an advanced stage of growth. 



During this period and for some time after, they have to encounter more 

 persevering and dangerous enemies than the ants or the fungus already alluded 

 to, in the various species of Tits. These birds appear to have a peculiar faculty 

 for discovering the deposited masses of seeds and bringing observations upon them 

 to an untimely end. This accounts also for the fact that considering the immense 

 number of Mistletoe berries, which are to be seen every year, few seeds are to be 

 found in an advanced stage of growth, and thus we have a good illustration of 

 Darwin's remark that "no fallacy is more common with naturalists than that 

 the numbers of an individual species depend on its powers of propagation." 



After the seed has been deposited and the viscous matter has disappeared, 

 the processes begin to push their way through the dead coverings. They advance 

 parallel to the bark until they attain the length of from ~\ to g of an inch. The 

 club-shaped end bending downward then becomes a disc, not unlike in section to a 

 boy's sucker. After some time, which has yet to be ascertained, a radicle descends 

 from the centi e of the disc and penetrates into the bark. The penetration of the 

 hark by the radicle is all the more remarkable because the cellular tissue of which 

 it is composed is so much softer than the liber of the tree, that in a few minutes 

 after a section is made, the tissue of the Mistletoe radicle shrinks so as to form 

 a hollow in the surface of the section. From an examination of the section 

 which fig. 5 represents, it appears that the radicle penetrates the epidermis of the 

 bark, in a pointed form, turning up the bark on allsides in advancing. On reaching 

 the cambial layer, it begins to swell into a spherical form, and in this shape 

 occupies the external layers of the alburnum. The tissue of the alburnum, 



