114 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
species. The second set of hybrids to illustrate the variability of second- 
ary hybrids and the law of Partial Prepotency consist of twenty-four 
plants, all raised from the same seed-capsule by Mr. Reginald Young, of 
Liverpool, out of P. Boxalli (Pfitz), var. atratum, by P. x politum, the latter 
being itself a hybrid between P. barbatum and P. venustum. (Figs. 33-38.) 
For the sake of convenience I will class these unflowered hybrids as 
forms of what I believe to be the original hybrid of the same parentage, 
viz. P. x Pluto, raised by Messrs. Low, of Bush Hill Park, using 
Roman numerals from I. to XXIV. to distinguish the individual varieties. 
The following diagram will show the pedigree at a glance :— 
DIAGRAM SHOWING THE Two Parents AND Four GRANDPARENTS OF 
PaPHIOPEDILUM x PxiuTO (vars.). 
P. P. | P. 
12 
| 
B. B. barbatum venustum 
3 2 
Hie: eae Fig. 36. A ere oe Fig. 38. 
1p. 12 
Boxalli x politum 
atratum 
3 f 
_ Fig. 33. Fig. 34. 
PapHiopEDILUM x PuuTo (vars.). 
According to the Galtonian law, these varieties of the hybrid P. x 
Pluto should show, on the average, } P. Boxalli + } P. x politum + } 
P. barbatum + } P. venustum; or to put it more simply, 4 P. Boxalli 
+ 1 P.barbatum + + P. venustum. 
The following facts will show the disturbing factor of Partial Prepo- 
tency in regard to the habit, form, and colour of the leaves. 
Prepotencies in Habit, Form, and Colour of Leaves. 
P. x Pluto, 1.—The parent P. Boxalli is prepotent in habit and form, 
while the grandparent P. venustum predominates in colour of leaves. 
P. x Pluto, 1I.—The grandparent P. venustum predominates in 
colour of leaves. 
P. x Pluto, ITI.—P. Boxalli alone predominates in habit, while P. 
Boxalli and P. venustum together preponderate in colour of leaves. 
P. x Pluto, 1V.—P. Boxalli alone predominates in habit, while P. 
Boxalli and P. barbatum together preponderate in colour of leaves. 
P. x Pluto, V—P. Boxalli predominates in form, while P. venus- 
tum preponderates in habit and colour of leaves. 
P. x Pluto, VI.—P. Boxalli predominates in habit, while P. venus- 
tum preponderates in colour of leaves. 
P. x Pluto, VIJ.—P. Boxalli predominates in habit and colour, 
while P. barbatum prevails in form of leaves. 
P. x Pluto, VIII.—P. Boxalli alone predominates in habit and form, 
while P. barbatum and P. venustum together preponderate in colour of 
leaves. 
