DR. HARLEY ON THE PARASITISM OF THE MISTLETOE. 191 
With reference to the size and number of their medullary rays, these plants may be 
arranged in the following order :— 
Vine. . . . . rays average th of an inch X 3È, crowded. 
*Maple -—- ^ 55 5 z1., crowded, more so in Maple. 
* Walnut 80 400 
Elder. ; as 9 zig] 
END v x a ET m ivo, large, but wide apart. 
*Plum. ES x as 34 no 
*False Acacia 
*Cherry Laurel » io » is 
*Portugal Laure 
EN com 9 d ^ — 
*Hawthorn } gs a .1-, numerous. 
* Apple and Crab e 129 5 123 
* Almond . » os 7 guo» numerous. 
Medlar » i59 وو‎ 900° 
*Lime UU الام‎ UM S وو‎ En EE) 180 0? wide apart. 
VO uo oig وو‎ iis چ وو‎ close. 
* Ash i 359 وو‎ 1 as 0 
*Poplar 
‘Willow Er » 109 " Taso 
Alder 
*Pear . وو عم‎ T zu ود‎ 3600" 
*Elm and Birch . » išo » raso Wide apart. 
*Fir i 1 
*Larch d 900 a te 
Lilac . وو‎ iv وو‎ dus 
*Oak 
*Beech | 33 59 " : 8 50 8 
Spanish Chestnut 
Hazel $n i 
R 150 » 2500 
Horse Chestnut 
The order in which the Mistletoe-bearing trees occur in the above series corresponds 
closely to the relative frequency of the attachment of the parasite to them. The apparent 
exceptions are due to two circumstances: Ist, the precariousness e pages m 
Viscum, the only means for effecting the process being extrinsical and accidental. The 
more closely, therefore, a tree is approximated to a fertile plant, the qe certainly will 
it be affected, and vice versd. The greater frequency with which the Mistletoe attacks 
Apple- and Hawthorn-trees, as compared with Maple- and Walnut-trees, which upon the 
* Plants upon which the Mistletoe spontaneously grows, or upon which it may be m 
0 
