ON VARIETIES IN PLANTS 311 
they include garden and forcing varieties which combine marvellous 
beauty of form and color with vigor and hardiness (Fig. 126a). Four 
or possibly five distinct species enter into the ancestry of the group, as 
shown by the following pedigree. The Hybrid Perpetuals (I*ig. 1266) 
are of mixed ancestry, all being hybrids of the Damask Rose (Fig. 126c) 
crossed either with Hybrid Bourbon or Hybrid Chinese varieties. 
The hardy, disease-resistant Japanese species, Rosa rugosa and R. 
wichuriana have entered into the ancestry of some of the best modern roses. 
Thus, the American Pillar variety is a hybrid between a red Hybrid 
Perpetual crossed with a hybrid between R. wichuriana and R. setigera, 
the Prairie Rose of America. Again, the Silver Moon variety is a result 
ADCaStrrcenes ea: derivatives of........... Rosa chinensis var. odoratissima 
Hybrid ve 
Rosa gallica 
Tee Hybrid 
a Hybrid va CE (French or Provence 
Perpetuals ee See Fig. 126d. 
‘ace Hybrid 
Bourbons Rosa chinensis 
Rose idwrarde wen Chinese Monthly 
or Bengal Rose). 
Rosa damascena 
(Damask Rose) Rosa centifolia 
(Cabbage Rose). 
Fieg.—127. Pedigree of the hybrid tea roses. 
of crossing R. levigata, the Cherokee Rose, with a hybrid between the 
Tea Rose, Devoniensis, and R. wichuriana. These examples will serve 
to illustrate the composite ancestry of our best roses. The practicability 
of this method of procuring new varieties has of course been enhanced 
by the possibility of vegetative propagation. Occasionally valuable 
varieties have arisen as bud mutations but these usually differ from the 
parent variety only in some definite character, like flower color or habit 
of growth. 
In passing it is of interest to note how extensively this method of 
variety creation has been used by horticulturists, particularly in species 
which are normally propagated by clonal multiplication. The hybrid 
varieties of the rhododendron rival in diversity and floral magnificence 
even those of the rose, and like them they have been derived from the 
mingling of a number of different species. But it is among the Rosacee 
particularly that horticulturists have found the most favorable subjects 
for hybridization. It is necessary in this connection merely to mention 
such familiar examples as varieties of plums, apples, strawberries, and 
other rosaceous fruits in the production of many of which extensive 
hybridization has been employed. In seed plants, also, there are many 
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