SCIENCE 



[N. S. Vol. XXXIII. No. 858 



remarkable form of dimorphism of the 

 gametes of several species of evening prim- 

 rose. If reciprocal hybrids are m.ade between, 

 say, (Enothera hiennis and 0. muricata, the 

 resulting hybrids are very unlike and strongly 

 patrocline, in both cases presenting only 

 slight traces of any influence by the female 

 parent. Detailed investigations now under 

 way by Professor de Vries show that the 

 ovules and pollen grains carry quite different 

 hereditary tendencies. The common (Eno- 

 thera hiennis represents the form inherited 

 through the pollen, the characters carried by 

 the ovules being recessive. If 0. hiennis is 

 crossed with pollen of another species over 

 which it is dominant, the result is to bring 

 into expression the form inherited through 

 the ovules, which de Vries calls the conica 

 form. This form is obtained if (Enothera 

 hiennis is crossed with pollen of 0. muricata, 

 0. Hooheri, 0. strigosa, etc. Similarly, if 

 (Enothera muricata is pollinated with 0. hien- 

 nis (Chicago form), 0. Hooheri and 0. stri- 

 gosa, it yields what de Vries calls the frigida 

 form which represents the form of 0. muri- 

 cata inherited through the ovules. 



The ordinary form of 0. hiennis represents 

 what de Vries calls the pollen picture of this 

 species, the pollen form {hiennis) being domi- 

 nant over the ovule form {conica). The same 

 is true of 0. muricata, the ovule form 

 {frigida) being recessive to the pollen form 

 {muricata). 



This property of producing gametes having 

 diverse hereditary qualities is termed by Pro- 

 fessor de Vries " Heterogamie," but as this 

 term is already used in many different senses 

 it seems best to propose instead a new term, 

 allogametism, after the analogy of such words 

 as allotropism. 



The pollen grains and ovules of (Enothera 

 hiennis and 0. muricata would constitute allo- 

 gametes. 



If B represents (Enothera hiennis, M, 

 (Enothera muricata, H, (Enothera HooTceri, 

 and L, (Enothera LamarcMana, the second 

 term being the male parent in each case, some 

 of the remarkable results of allogametism are 

 as follows: 



Hybrid BM = comica (ovule picture of 0. bien- 

 nis). 



Hybrid MB = hiennis (pollen picture of 0. bien- 

 nis). 



Hybrid MS.^ frigida (ovule picture of 0. muri- 

 cata) . 



Hybrid LM = muricata (pollen picture of 0. 

 muricata). 



In such allogametic species of (Enothera 

 the diversity of the gametes of the two sexes 

 does not become apparent unless reciprocal 

 hybrids are made with another species, 

 whereupon very different results are obtained, 

 depending upon which species is used as the 

 female parent. 



In case the reciprocal hybrids of the same 

 two parents are crossed, what de Vries calls 

 double reciprocal hybrids result, thus 



BM X MB = B, 

 MB X BM = M. 



In such cases the " peripheral " ' grand pa- 

 rent shows complete dominance, while the 

 " central " ^ grand parent is eliminated, thus : 



B(M) X (M)B = B, 

 M(B) X (B)M = M. 



If a patrocline hybrid is crossed with pollen 



of the paternal species, what de Vries calls 



■ iterative hybrids result, exactly like the first 



hybrid and very like the paternal species, thus : 



MB X B = MB = B, 

 B X BM = BM = M. 



The central term in the formula is elimi- 

 nated in this case, M(B)XB = MB = B. 



If a patrocline hybrid be crossed with pollen 

 of the mother species, what de Vries calls 

 sesqui-reciprocal hybrids result in which the 

 grandpaternal species is eliminated, thus : 



MB X M = M, 

 BM XB = B. 



The central term in the formula is again 

 eliminated, M(B)XM = ]\I. 



Not all the characters of the species were 

 found to be transmitted allogametically. In. 



' So called from the position in the above for- 

 mulae. 



