12 



INTRODUCTION. 



Ihe other parent form ; or in the Spring their leaves re- 

 semble the one, and in the Autumn the other type (Cistusj 

 Populiis) ; or the flower-coloring is altered during the fall 

 of the bloom (as in Melandryum album X M. rubrum, 

 Epilobium roseum X -E. montanum, lantana) or in the 

 Autumn (as in Nicotiana rustica X N. tabacum, Tropceo- 

 lura. Lobelia, etc.), sometimes also in different years (as 

 in Bletia crispa X B. dnnabarina, Galium dnereum X G- 

 verum). In the crossing of races, rarely of hybrids in a 

 strict sense, one finds now and then the properties of the 

 parents unblended and side by side (as in Cucumis melo, 

 the thominess of the Datura fruits, the flower-coloring of 

 Rhododendron rhodora X R- calendulaceum, R. ponti- 

 cum X R- flavum, Anagallis, Linaria vulgaris X L. pur- 

 purea. Calceolaria, Mimulus, Mirabilis). The flower- 

 coloration often behaves in unexpected ways. The hy- 

 brids of Verbascum phmniceum, while having similarity 

 of form, are very variable in the flower colorings. In 

 Helianthemum hybrids variously colored flowers have 

 been found on the same stem. 



Frequently, from the crossing of nearly related races, 

 especially color varieties, plants are produced which are 

 exactly like or closely resemble one of the parent races, 

 as in Brassica rapa var., Linum, Pisum, Phaseolus, Aruv- 

 gallis, Atropa, Datura stram,monium. Salvia hormium, 

 etc. In the second generation the influence of the other 

 parent race is usually flrst disclosed by a part of the 

 seedlings reverting to it completely, or only in certain 

 definite properties. Only in Atropa a reversion to the 

 unstable yellow form has not been noted. 



In many cases the hybrid is so like one of the parent 

 forms that it could be considered as a very slight varia- 

 tion of the same. In the crossing of widely separated 

 species the overwhelming influence of one parent species 

 shows itself in the hybrids in a striking manner. Thus, 

 the cross of Dianthus armeria X D. deltoides is much 

 nearer to D. deltoides, of D. caryophyllus X D. chinensis 

 to D. caryophyllus, of Melandryum rubrum X M. nocti- 

 florum, to N. rubrum, of Verbascum blattaria X V- 

 nigrum to V. nigrum, and of Digitalis lutea X D. pur- 

 purea to D. lutea, than to the second species. 



Occasionally the hybrids of the flrst generation show 

 properties which are entirely different from those of 

 both parent species. This is particularly noticeable in 

 the colors of the flowers. The most noteworthy example 

 of this is the blue-blossomed hybrids of the white Datura 

 ferox with the equally white species D. Imvis and D. 

 strammonium bertolonii. Instances of unexpected blos- 

 som-coloration are numerous in hybrids of species with 

 colored flowers, in which the hybrids in no way show 

 the coloring which one would expect from a mixture of 

 the pigments of the parents, as in Clematis recta X 

 C. integrifolia, Aquilegia atropurpurea X 4. canadensis 

 (and others). Anemone patens X A. vernalis. Begonia 

 dregei X B- sutherlandi (and others), Nicotiana suaveo- 

 lens X N. glutinosa, Verbascum pvlverulentum X ^• 

 thapsiforme, and in hybrids of C. phwniceum which are 

 especially good examples. In the crossing of races prop- 

 erties appear many times which do not resemble the 

 parent forms but other races of the same species, as in 

 Papaver somniferwm and Datura strammonium. The 

 hybrid Nicotiana rustica X N. paniculaia shows at times 

 the flower coloration of N. texana, a foreign subspecies of 



N. rustica. Other properties which in the hybrids are 

 developed to a greater degree than in the parent forms 

 are, for example, the greater stickiness of several hy- 

 brids of Nicotiana (N. rustica X N. paniculata) ; the 

 apparently greater abundance of honey in the hybrid of 

 N. rustica X N. paniculata; the stronger of the nauseat- 

 ing odor of the hybrids of Melandryum viscosum; and, 

 according to Kuntze, the alleged much larger quantity of 

 quinine ( ?) in the hybrids of Cinchona. 



In later generations the offspring of the hybrids show 

 still further variations from the properties of the parent 

 species. 



Thibd Peoposition. 



Hyhridg hetween different races and species are, as a rvle, 

 differentiated from specimens of a pure race by their' 

 vegetative power. Hybrids between widely separated 

 species are frequently very weak, especially when young, 

 so that the raising of the seedlings is rarely successful. 

 Hybrids between more closely related species and races are, 

 on the other hand, uncommonly luxuriant and strong, 

 these qualities mostly shoieing themselves in size, quick- 

 ness of growth, early blooming, luxuriance of bloom^, longer 

 dwatiom of life, great power of reproduction, exceptional 

 size of some particular organs, and in analogous pecu^ 

 Uarities. 



In support of this proposition it will be necessary to 

 refer to several examples : Delicate seedlings, it is stated, 

 follow from the crossing of Nymphcea alba with foreign 

 species. Hibiscus, Rhododendron rhodora with other spe- 

 cies, Rh. sinenses with Eurhodendren, Convolvulus, hy- 

 brids resulting from species of Salix where a species and a 

 hybrid or two hybrids are crossed, Crinum and Narcissus. 

 The fact that embryo plants from the fertilized seeds 

 of hybrids are delicate and difficidt to raise is, moreover, 

 frequently noted. Dwarfed growth is seldom noted in 

 hybrids, except in some of the hybrids of Nicotiana, espe- 

 cially N. quadrivalio X N. tabacum macrophylla. Giant 

 growth is, on the other hand, more frequent, as in Ly- 

 cium. Datura, Isoloma, Mirabilis. In size, the hybrids 

 usually exceed both parent species, or are of a height that 

 is the average of the heights of the parents, as in many 

 hybrids of Nicotiana, Verbascum, Digitalis. Develop- 

 ment often proceeds with striking rapidity. Klotzsch 

 emphasizes the rapidity of growth of his hybrids of 

 Ulmus, Alnus, Quercus, and Pinus. They often flower 

 earlier than the parent species, as in Papaver dubium X 

 P. somniferum; in many Dianthus hybrids (Focke's 

 cross, D. arenarius 9 "X. D. plumarius S , showed no in- 

 clination to flower earlier than the parents) ; Rhodo- 

 dendron arbor eum X Rh. catawbiense, Lycium, Nicoti- 

 ana rustica X N. paniculata. Digitalis, Wichura's six- 

 fold Safe-hybrid, Gladiolus, Hippeastrum vittatum X 

 H. regince, and so forth, and particularly many hybrids of 

 Verbascum. On the other hand, there are also several 

 hybrids which do not flower at all or only after a long 

 time, as in the genera Cereus and Rhododendron. Of 

 the earlier ripening of seeds unconnected with earlier 

 flowering, I know, at present of but one example, in 

 Nuphan: Very frequently, an extraordinary wealth of 

 bloom has been noticed, as in Capsella, Helianthemum, 

 TropcBolum passiflora. Begonia, Rhododendron, Nico- 

 tiana {N. rustica X N. paniculata, N. glutinosa X N. 

 tabacum, and others) ; Verbascum, Digitalis, many Ges- 

 neracecB, Mirabilis, and Cyripedium. The flowers are 

 very frequently larger in hybrids. In the crossing of 



