538 Farmer . — On the Structure of a Hybrid Fern . 
known that vigorous sports are sometimes highly sterile, and 
this circumstance, coupled with the frequent luxuriance in 
vegetative development of sterile leaves, has given rise to 
a doctrine of correlation which is doubtless a neat way of 
expressing the facts, but which in reality leaves us exactly 
where we were before. It seems, however, not altogether 
improbable that an extended experimental study of dimorphic 
Fern-leavfes might well prove to be one of the avenues leading 
to a clearer conception of the essential differences between 
what we at present term vegetative and reproductive activity. 
Regarding the plant now under discussion from another 
aspect, there are some interesting points of contact between it 
and other hybrids, as for example the famous Cytisus Adami. 
The latter, as is known, is a hybrid between’ the arborescent 
C. Laburnum and the shrubby C. purptireus, although it is 
by no means agreed as to whether it arose as a seminal or 
a graft hybrid. The authority for the latter origin rests 
chiefly on the statements made by Adam, and on the failure 
of all attempts to cross the two parent forms. 
The C. Adami produces on the same plant flowers and 
shoots which may be roughly referred to three categories 1 : — 
1. The hybrid flowers, intermediate between the two 
parents, and often highly variable. 
2. Flowers closely resembling the Laburnum , and these 
are commonly borne on specially vigorous shoots. 
3. Shoots with flowers and leaves of the purpureus type. 
Now the regular Adami flowers are sterile. The pollen is 
indifferent, and the ovules, according to Caspary, are monstrous 
and incapable of fertilization. But the two reverting forms 
can both set good seed from which new plants can be raised. 
And although the seedlings thus obtained closely resemble 
the parent form to which the seed-bearing shoot had reverted, 
it is clear that they have not purged themselves of their 
mixed origin, since Herbert 2 , while hinting at a certain 
1 See description (with coloured plates) by Edouard Morren in La Belgique 
Horticole, 1871. 
2 Herbert, Journ. Hort. Soc., vol. ii. 
