Dkcembeb 16, 1904.] 



SCIENCE. 



849 



consists in the fusion of the sexual nuclei to- 

 gether with the cytoplasm of the gametes.' 

 In Chapter III. fecundation by non-motile 

 isogametes is considered, as illustrated by 

 Sporodinia, Glosterium, Cosmarium, the Dia- 

 toms (Rhopalodia, Cocconeis) and Basidio- 

 bolus. In Chapter IV. the heterogamie 

 fecundation of Sphwroplea, the Fucacese, 

 Volvox, CBdogonium, Coleochwte, Vaucheria_, 

 Albugo, Achlya and Saprolegnia are discussed. 

 Then follow chapters on ' the tjrpe of the 

 Ascomycetes and Ehodophycese (V.), 'the 

 Archeg-oniates ' (VI.), inekiding Pteridophyta 

 and Gymnosperms, and ' Angiosperms ' (VII.). 

 'In this last chapter the author says, 'the view 

 held here is that pollen grains and embryo-sacs 

 are respectively micro- and macrospores.' 

 Here the author has permitted some confusion 

 to creep into his usually lucid text, for a 

 little later he uses the expression ' the embryo- 

 sac or female gametophyte ' (pp. 169 and 173). 

 Certainly an embryo-sac can not be both 

 macrospore and female gametophyte. A vol- 

 uminous bibliography, including 187 titles, 

 closes the paper, which can not but prove to 

 be very useful to botanical teachers and 

 students. 



TECHNICAL MYCOLOGY. 



Seven years ago Doctor Franz Lafar, pri- 

 vate docent in the technical high school at 

 Ilohenheim, issued the first part of a most 

 iiseful work under the title ' Technische 

 Mykologie.' About a year ago the second 

 part appeared, and with it the announcement 

 that the present edition was to be discontinued, 

 and that a second, much enlarged edition was 

 to be undertaken immediately. Of this new 

 edition the first Lieferung of 160 pages has 

 just appeared. It includes an introduction 

 of 28 pages — mostly historical — ^by Dr. Lafar, 

 followed by 121 pages by Dr. Migula devoted 

 to the bacteria. Near the close of the 

 Lieferung we have the beginning of Dr. 

 Lindau's treatment of the true-fungi (Eumy- 

 cetes). If one may judge from these pages, 

 this edition is to be a notable addition to 

 mycological literature. From the prospectus 

 it is learned there are to be five volumes, the 

 first of which is to be devoted to the general 



morphology and physiology of the fungi. The 

 succeeding volumes are to be more or less 

 technical, dealing with the relation of the 

 fungi to various industries, the soil, water- 

 supply, etc. 



PARTHENOGENESIS IN PLANTS. 



In a recent number of the Bericlite der 

 deutschen Botanische Gesellschaft (Vol. 

 XXII.), Dr. J. B. Overton describes the 

 cytology of parthenogenesis in Thalictrum 

 purpurascens, a common American weed. The 

 author has prepared a summary of this paper, 

 as follows : 



In a previous experimental and morphological 

 study the author discovered that this plant sets 

 seed freely in the absence of pollination and that 

 the embryos could develop normally from fertil- 

 ized egg-cells and also parthenogenetlcally from 

 unfertilized egg-cells. In the present investiga- 

 tion the author studied the cytologieal phases of 

 the subject. He was able to determine that the 

 number of chromosomes was reduced by one half 

 In the pollen-mother-cells by means of the hetero- 

 typical mitosis. Similar conditions were also 

 found in the typical embryo-sac mother-cell, 

 which gives rise to true tetrads. He also found 

 in exceptional cases embryo-sac mother-cells in 

 which no reduction takes place. The division, in- 

 stead of being heterotypical, appears to resemble 

 both vegetative and heterotypical mitoses. This 

 division, therefore, represents a transitional stage 

 between the ordinary somatic and the hetero- 

 typical divisions. Instead of twelve chromosomes, 

 the reduced number, the spindle shows twenty- 

 four chromosomes. In those embryos which devel- 

 oped from normally fertilized eggs as well as those 

 which developed parthenogenetlcally, he found 

 twenty-four chromosomes. Twenty-four chromo- 

 somes were always found in purely vegetable cells. 

 The author concludes that only those eggs with 

 the somatic number of chromosomes are able to 

 develop parthenogenetically, while those which 

 contain the reduced number of chromosomes must 

 be fertilized. The works of .Juel and Murbeek 

 show that Antennaria alpina, several species of 

 Alchemilla and Taraxacum officinale, have ac- 

 quired the habit of complete parthenogenesis. 

 Thalictrum purpurascens has only partly attained 

 the power of propagating itself parthenogenetic- 

 ally. The author believes it possible that the 

 failure of pollination, due to a separation of 

 staminate and pistillate plants, has acted as a 

 stimulus to final parthenogenetic development. 



