12 



INTRODUCTION. 



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

 scnibli the one, and in the Autumn the othei fcype(< 'isius; 

 ; 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 

 AutuD .1 Nicotiana rustical N. tabacum, Tropceo- 



lum, I etc.), sometimes also in different years (as 



in Bletia crispa X B. cinndbarina, Galium i ineri wm X 0. 

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

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

 parents unblended and side by side (as in ( 'ucumis 

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

 Rhododendron rhodoraX H. calendulaceum, R. politi- 

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

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



ati /I'teii behaves in unexpected ways. The hy- 

 lirids of Verbascum phomiceum, 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, Ana- 

 gallis, Atropa, Datura strammonium, Salvia hormium, 

 etc. In the second generation the influence of the other 

 parenl race is usually first, 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 

 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 P. deltoides, of D. cnri/ophyllus X D. chinensis 

 to P. caryophyllus, of Melandryum rubrum X -V- nocti- 

 florum, to X. rubrum, of Verbascum blattaria X l r - 



./,' to V. nigrum, and of Digitalis luteal D. pur- 



• io P. lutea, than to the second species. 



una. ally the hybrids of tin' first 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. Icevis and P. 

 strammonium bertolonii. Jnstaneev of unexpected bios 

 som-coloration are uumerous in hybrids of species with 

 colored flowers, in which the hybrids in no way show 

 hieli one would expect from a mixture of 



pigments of the parents, as in Clematis rectaX 

 C. integrifolia, Aquilegia atropurpurea X A. canadensis 



I others), Anemone patensX A. vemalis, Begonia 

 dregei - B. sutherlandi (and others), Nicotianasv 



< N. glutinosa, Verbascum pulverulentum X N. 

 thapsiforme, and in hybrids of C. phceniceum 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 imi - . as in 

 Papaver somniferum and Datura strammonium. The 

 bvbnd Nicotiana rustica X X. paniculata shows at times 

 the flower coloration of A", texana, a foreign sul 



N. rustica. Other properties which in the hybrid 

 developed to a greater degree than in the parent E 

 aie. for example, the greater stickiness o ral hy- 



brids of Nicotiana (A. < N. pa) • : the 



apparently greater abundance of honey in rid of 



\. rush,, i ■ N. paniculata; the stronger of the 

 ing odor of the hybrids of Melandryum viscosum; and, 

 according to Kuntze, the alleged much larger quantity of 

 quinine ( ?) in the hybrids of ( 'inchona. 



In later generations the offspring of the hybrids show 

 -till further variations from the propet the parent 



ies. 



TlIIHD PltOI'OSITION. 



Hybrids between different races and species are, as a 



differentiated from specimens of a pure race by their 

 vegetative power. Hybrids between widely separt 

 species tin frequently very weak, especially alien young, 

 no Unit the raisin;/ of tin g< , ill i ngs is rarely successful. 



Hybrids between more oloi • ly i • lated species and races a . 

 on the other hand, uncommonly luxuriant and strong, 

 these qualities mostly showing themselves in size, quick- 

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

 duration of life, great power of reproduction, exceptional 

 size of some particular organs, and in analogous pecu- 

 liarities. 



In support of this proposition it will be necessary to 

 refer to several examples: Delicate seedlings, it i- -; 

 follow from the crossing of Nymphcea alba with foi 

 species, Hibiscus, Rhododendron rhodora with other spe- 

 cies, Rh. sinenses with Eurhodendren, Ci nvolvulus, 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 difficult 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- 

 i in in. Datura, Isoloma, Mirabilis. In size, the hybrids 

 usually exceed both parent species, or are of a hi 

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

 hybrids of A" icotiana, Verbascum, Digitalis. Develop- 

 ment often proceeds with striking rapidity. Klotzsch 

 emphasizes the rapidity of growth of his hybrid- of 

 Vlmus, Ahins. Quercus, and Pinus. They often 

 earlier than the parenl species, as in Papa wm X 



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

 cross, P. arenarius 9 X D. plumarius s , showed no in 

 dilution to flower earlier than the parent-); Rhodo- 

 dendron arboreum X Bh. catawbiense, Lycium, Nicoti- 

 ana rusticaX N. paniculata, Digitalis, Wichura's six- 

 fold ,s'i//i.r-hybrid, Hiadiolus, Hippeastrum vittatum X 

 //. reijiinr, 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 

 Nuphar. Very frequently, an extraordinary wealth of 

 bloom has been noticed, as in Capsella, Helianthemum, 

 'idiiiu passiflora, Begonia, Rhododendron, Nico- 

 tiana (N. rustica X N. paniculata. X. olulinosaX N. 

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

 neracece, Mirabilis, and Cyripedium. The flowers are 

 very frequently larger in hybrids. In the crossing of 



