March 15, 1900] 



NA TURE 



471 



But Nawaschin and Guignard have further shown that, 

 in addition to the normal fertilisation of the egg-cell by 

 one of these pollen-nuclei (spermatozoid), the other 

 spermatozoid fuses with the upper polar nucleus of the 

 embryo-sac, and thus brings about a sort of secondary 

 fertilisation— a fertilisation of the cell which, by further 

 division, produces the endosperm. For it will be re- 

 membered that the secondary nucleus arises by the 

 fusion of the two polar nuclei. 



Divested of details, while one spermatozoid nucleus 

 carries material from the pollen into the egg-cell, and so 

 transfers the influence of the male to the egg and its 

 resulting embryo-plant, the other spermatozoid carries a 

 similar share of material from the pollen into the polar 

 nucleus, and thus transfers the influence of the male to 

 the secondary nucleus of the embryo-sac, and thus to the 

 endosperm. 



Now the endospermjs regarded as the representative of 

 the prothallus of the higher Cryptogams, and acts as the 

 nurse for the embryo ; and the upshot of the foregoing 

 is that not only is the embryo (and through it the future 

 plant) affected by the male hereditary substance, which 

 can be easily seen eventually in cross-bred plants and 

 hybrids of all sorts, but the rudimentary prothallus genera- 

 tion also receives its dose of male substance, and the 

 question arises whether the effect of this dose can be 

 traced in any visible way. 



Let us now turn to another set of events. It has 

 been known for some time that different varieties or races 

 of the maize or " Indian corn," although all belonging to 

 the same species, show remarkable differences, not only 

 in the size, shape, colour, &c., of their well-known grains, 

 but also in the nature of their nutritious contents — i.e. 

 what is usually termed the "flour" or "meal." Now, 

 this "flour" is the endosperm, and contains the nutritious 

 substances for the growing embryo. In the typical case 

 its cells are crammed with starch grains, well known in 

 domestic economy as " corn-flour." But in certain races 

 of maize there are no (or very few and small) starch 

 grains, but a slimy substance (dextrin ?), mixed with 

 sugar, fills the cells. Again, the outermost layer of cells 

 bounding the endosperm — the so-called aleurone layer 

 —has, not starch grains, but nitrogenous reserve stores 

 for its principal contents, and in some races bright 

 purple or other colouring material as well, which shines 

 through the skin of the grain (testa and pericarp), and so 

 gives the hue to the fruit. 



The economical importance of the maize' has stimu- 

 lated many observers to experiment in hybridising the 

 existing races, and the principal object of this article is 

 to show how some recently observed results in this con- 

 nection have— quite unexpectedly— come ro cast new 

 lights on the phenomena above referred to, and to illus- 

 trate the potency of pollen in a way not hitherto 

 suspected. 



These researches are due to De Vries,'-and to Correns,'' 

 who have found that if cross-breeding is carried on 

 between races of maize with a starchy yellow endosperm 

 and violet aleurone layer, and races with a sugary hyaline 

 endosperm and colourless aleurone layer, for instance, very 

 marked effects of the pollen can be traced in the endo- 

 sperm of the directly resulting grain, quite apart from 

 the effects eventually discernible in the resulting cross- 

 bred plant to which the embryo gives rise, and which, of 

 course, are only visible in the succeeding crop. These 

 visible effects of the pollen are expressed only in the 

 colour and chemical contents of the endosperm. 



1 The meal is used for Polenta, corn-flower, pop-corn, &c., and after the 

 m.-inner of malt in distilling spirits. The young grains are cooVed. The 

 ^ugary sap is used for fermented drinks, Chica, Pulque de Mahiz, &c. The 

 fraw for paper, &c. The raw grain, young shoots, &c., for lodder. Some 

 loes are of horticultural value, and soon. In 1893, 32,000,000 cwts. were 

 nported into this country(see "Official Guide to the Museums of Economic 

 liotany, Kew." No. 2, 1893, p. 64). 

 - Comptes rendus, ^Ii2l<)<), No. 23. vol. cxxix. p. 973. 

 3 Bet. d. d. JSot. Ces. 1899, vol. xvii. p. 4x0. 



NO. 1585, VOL. 61] 



Thus, the result of pollinating a race (A) which has a 

 colourless aleurone layer, by a race (B) with a coloured 

 one, may be that the ripening grain of A now obtains an 

 endosperm with its aleurone layer the same colour as B ; 

 or if A has a starchy endosperm and B a slimy and 

 sugary one, the endosperm of A becomes slimy and 

 sugary, and so on. 



The effect of the pollen of B, so directly expressed in 

 the resulting endosperm of A, does not necessarily show 

 itself in the converse case, however ; and if the pollen of 

 B alters the colour of the aleurone layer in the grain of 

 A, the effect of the reciprocal cross may be that the 

 pollen of A alters — not the colour of the aleurone, but — 

 the contents of the endosperm of B, e.g. from starchy to- 

 sugary, and so on. 



Correns points out that no visible change in the 

 embryo, or in the size of the endosperm, or size and 

 shape of the grain can be thus directly produced — 

 whatever may be the more distant eflfects visible in the 

 cross-breed resulting from the sowing of the grain next 

 year. 



There seem to be two possible ways of explaining 

 these remarkable phenomena. 



First, we may suppose that the spermatozoid nucleus 

 of the pollen tube, having fused with the egg-cell, so 

 alters the embryo that as it grows it affects the endo- 

 sperm {e.g. by secreting some enzyme) and so alters the 

 colour of the aleurone layer on the nature of the cell- 

 contents ; this hypothesis is supported in part by the 

 fact that while it is easy to produce sugary endosperms 

 in grains of races which normally develop starchy ones, 

 the converse action is not obtained. 



The second hypothesis is that we have in these pheno- 

 mena the direct visible effects of the fusion of the 

 second pollen tube nucleus (spermatozoid) with the polar 

 nuclei (from which the endosperm results). In other 

 words, we have here a hybrid endosperm as well as a 

 hybrid embryo. 



Both De Vries and Correns regard the latter explana- 

 tion as the right one, and Correns points out that similar 

 cases have been observed by Giltay in rye. 



On the other hand, no visible results in the endosperm 

 were obtained in peas and lilies, and the deep blue 

 colour of the yellow seeds of species of Lcucojutn or of 

 Peas crossed with the pollen of deep blue seeded races 

 of the same in each case depends on the formation of 

 blue proteid grains in the epidermis of the cotyledons. 



That these positive results will lead to renewed investi- 

 gations of other cases of nuclear fusion— t'.^. graft- 

 hybrids and other examples of the reactions between 

 scion and stock —may be confidently predicted, and in- 

 teresting discoveries must await us. My present object 

 is to call attention also to this excellent example of the 

 reciprocal advantages botanical science obtains by the co- 

 operation of workers in two totally different fields — the 

 results from the laboratory here throwing suggestive 

 lights on those from the seed-bed and garden, and vice 

 versa. (See, also. Address to Botanical Section of 

 British Associatibn, Toronto, 1897, p. 3.) 



H. Marshall Ward. 



ATMOSPHERIC ELECTRICITY AND 

 DISEASE. 



LAST summer I had the honour of making the 

 acquaintance of Dr. Schliep, of Baden-Baden. He 

 is well known to English medical specialists. He urged 

 me to design a recording electrometer, such as would 

 enable medical men to study atmospheric electricity. I 

 found that he himself had made daily observations for 

 twenty years, using a gold-leaf electroscope, which 

 enabled him to say whether the air had strong or weak, 

 positive or negative, electric potential, at the end of a 



