Notes on Pollen. Bij Lord Aveburi/. 477 



burger asserts that in Cupressus one pollen-tube may fertilize 

 several ovules.* 



In Malvaceae, according to Kerner,t the pollen-tube does not 

 reach the ovule, but the contents escape and travel down the style 

 in an elongated mass, destitute of v^all, like the plasmodium of a 

 Myxomycete. 



In Pimis, and in flowering plants generally, the pollen-tube, as 

 already mentioned, enters the ovule. In Zamia, Cycas, and Ginkgo 

 the pollen-tube never comes near the actual ovule, but the nucleus 

 is provided with ciJia, which carry it to its destination. This most 

 interesting discovery we o^^'e to a Japanese botanist, Hirase. % 



According to Blackman, excepting in the possession of cilia, 

 and in size, the antherozoids of Cycads do not seem to differ mate- 

 rially from the generative cell of Pinus. 



One of tlie most interesting and remarkal^le results of recent 

 investigations has been the discovery that the nucleus of all animal 

 and vegetable cells contains, besides the nucleus, a certain nvimbev 

 of solid bodies which can be stained, and thus rendered visible, by 

 reagents. They have been named chromosomes by Waldeyer. § 

 These appear, though the statement does not yet seem absolutely 

 proved, to be the same in numl;)er in all body-cells of each 

 species, and, for a reason which will be evident in a moment, 

 are always an even number. The numbers vary from four to over 

 a hundred. 



In the rat, the onion, and some other species, there are sixteen, 

 in Pinus there are said to be twenty-four. This is the number given 

 by Overton, who has been confirmed by Blackman. It is, however, 

 by no means easy to determine the exact number. As to those of man 

 there is much difference of opinion. In the most recent memoir on 

 the subject, that by H. von Winiwarter, || there are forty-eight chro- 

 mosomes in the female somatic cells. In men, on the contrary, he 

 states that there are only forty-seven. Some male insects are also 

 stated to have an unequal number of chromosomes in the generative 

 cells. If these statements are correct the fact is very remarkable. 

 The chromosomes must be very complicated structures. 



On the other hand, in the reproductive organs the divisions of 

 the cells reduces the number, as, for instance, in the pollen, the 

 ovule, and the egg-cell, to one half, but the process of fertilization, 



* Neue Unt. u. d. Befruchtungs-vorgang bei den Phanerogamen. Jena, 1884, 

 p. 53. t Nat. Hist, of Plants, ii. p. 410. 



X " On the Spermatozoid of Ginkgo biloba" Bot. i\Iag. Tokio, x. (1896). 

 " Etude s. 1. fecondation et I'Embryogenie du Gitikgo biloba," Journ. Coll. Sci. 

 Imp. Univ. Japan, 1895, also Ikeno, S., " Unt. u. d. Entw. d. Geschlechts organ 

 bei Cycas revoluta," Journ. Coll. Sci. Imp. Univ. Japan, 1890. See also Jahrb. 

 wiss. Bot., xxxii. heft 4 (Leipzig, 1898), and Webber, H. J., " Spermatogenesis of 

 Zamia and the PoUen-tube App. of Ginkgo," U.S. Dep. Agric. Washington, 1901. 

 " Div. of the Antherozoids of Zamia," Bot. Gaz. Chicago, 1897. 



§ Arch. Mikr. Auat.,.1888. I || Arch, de Biologic, 1912. 



