SHARE OF THE PARENTS IN BUILDING UP THE OFFSPRING 



59 



comprehensive and at the same time exceedingly careful experiments 

 recently made by C. Correns with Zea Mats ; it is only necessary to 

 look through the beautiful figures with which his work is adorned 

 to be convinced that heads of maize whose blossoms have been dusted 

 with the pollen of a different kind produce more or less numerous seeds 

 of the paternal kind, usually mingled with those of the maternal. 

 Thus heads of the variety Zea alba resulting from fertilization with 

 Z. cyanea exhibited a majority of white grains, but among them 

 a smaller number of blue; and the converse experiment, of dusting 

 Z. cyanea with the pollen of Z. alba, yielded heads in which a minority 

 of white grains appears among a majority of blue. But it is always 



Fig. 82. Fertilization in the Lily {Liliiim martago)i), after Guignard. A, the 

 embryo-sac before fertilization ; sy, synergidae ; eiz, ovum ; op and up, upper and 

 lower * polar nuclei * ; ap, antipodal cells. B, the upper part of the embryo-sac, 

 into which the pollen-tube (pschl) has penetrated with the male sex-nucleus 

 {6Jc) and its centrosphere ; below that is the ovum-nucleus (? k) with its (also 

 doubled) centrosphere {csph). C, remains of the pollen-tube (^jsc/^Z) ; the two 

 sex-nuclei are closely apposed. Highly magnified. 



only the nutritive layer surrounding the embryo — the endosperm — 

 which exhibits the character of the paternal species, and even the cap- 

 sule surrounding the seed shows nothing of it, but is purely maternal. 

 Thus the heads of different species with pale-yellow capsule, when 

 dusted with the pollen of Z. rubra, never have red seeds like those of 

 Z. rubra, but always seeds with a pale-yellow skin, while, in the eon- 

 verse experiment, dusting of the red-skinned species Z. rubra with 

 pollen from Z. vulgata, all the seeds are red, like those of the maternal 

 species, and the influence of the paternal species only shows when the 

 strong red skin has been removed, so that the intense yellow colour 

 of the endosperm, which in the pure maternal species is white, is 

 exposed to view. Thus the mysterious influence of the pollen never 



