THE CAUSE OF UNIONS. 85 



Betinospora, etc. ; but both kinds of foliage -not infrequently 

 appear together on the same plant; and, when this is the 

 case, the spinescent and free leaves are borne on relatively 

 less vigorous branches, the adherent foliage being charac- 

 teristic of the more vigorous and quick-growing terminal 

 shoots. It has been also noticed by Dr. M. T. Masters that not 

 only do the broad and free leaves of Juniperus and Betinospora 

 not occur on the leader shoots, but when the plant is varie- 

 gated then free leaves (on the stem with arrested growth) 

 are much more variegated than they are on the quick-grow- 

 ing leader shoot.* The last-mentioned observer has also 

 noticed that the free foliage is characteristic of the younger 

 condition of the plant, the adnate foliage that of the adult 

 state. 



The conclusions arrived at by Mr. Meehan are as follows : 

 (1) The true leaves of ConifercB are usually adnate with the 

 branches. (2) Adnation is in proportion to vigour in the 

 genus, species, or in the individuals of the same species, or 

 branches of the same individual. (3) Many so-called dis- 

 tinct species of Coniferm are the same, but with their leaves 

 in various states of adnation. 



Another very common form of adhesion, to which I have 

 already alluded and which is most probably due to hyper- 

 trophy through succulency at an early stage, is fasciation.f 

 Under this condition the fibro-vascular cylinder of at least 

 two " axes," which would be normally separate, coalesce, 

 and form an oval cylinder with, it may be, only a slight 



♦ Gard. Chron., 1883, vol. xix., p. 657. 



t For remarks on this phenomenon the reader is referred to Dr. 

 Masters's Teratologxj. It is particularly common in herbaceous plants, as 

 Lettuces, Asparagus, etc., and not unfrequent in Ash-trees. I observed 

 a trailing plant of Cotoneaster growing over a rockery by the side of a 

 stream in a garden, almost every branch of which was fasciated. 



10 



