XOTES AND ABSTRACTS. 



895 



to fix their special characteristics, so that they would continue to repro- 

 duce faithfully. Most of our common vegetables have been improved 

 from wild straggly plants of an almost fixed type to the nearly perfect 

 forms of dozens or even hundreds of types now grown. The writer refers 

 to the Tomato as being one of the most noticeable plants for illustration, 

 and says that it has been improved by selection in the short time of little 

 more than a generation from a weedy plant bearing small seedy fruit to 

 its present perfection, and scores, and even hundreds, of varieties. While 

 we have in this plant one that is susceptible to improvement, on the other 

 hand it is one that degenerates just as easily. The article infers that the 

 combined results of selection of natural improvements and careful breed- 

 ing have given us the great improvements in types of economic plants 

 with which we open the twentieth century. — H. G. C. 



Sequoia sempervirens, The Gametophytes, Arehegonia, 

 Fertilisation and Embryo of. By Anstruther A. Lawson (Ann. Bot. 

 xviii. Jan. 1904, pp. 1-22, plates i.-iv.). — A detailed account of the develop- 

 ment of the gametophyte generations and fertilisation phenomena. 



The reduction division of the macrospore mother-cell takes place in 

 March. A primary and secondary prothallus is distinguished : the 

 former arises as the result of free nuclear division, and simultaneous cell- 

 wall formation ; in it the archegonia are formed. 



The nuclei of both male cells are functional. Daring fusion the 

 chromatin of both sexual nuclei are in the spireme stage. It is believed 

 there are sixteen chromosomes in the gametophyte and thirty- two in the 

 sporophyte. — .4. D. C. 



Sigillariopsis in the Lower Coal Measures, On the occurrence 



Of. By D. H. Scott (Ann. Bot. xviii. July 4904, p. 519-521).— Hitherto 

 no fossil referable to the genus Sigillariopsis has been described besides 

 S. Decaisnei. The author describes two specimens occurring in the 

 calcareous nodules from the Lower Coal Measures of Lancashire. They 

 differ somewhat from Renault's specimens, and the name S. sulcata is 

 given. -A. D. C. 



Siphonese, Studies on. By A. Ernst [Beili. Bot. Cent. xvi. pp. 

 199-236, three plates; also pp. 367-382, with one plate). — The author 

 continues the detailed studies of the Siphonece which were begun in 

 vol. xiii. The present papers contain many interesting details. A 

 new species of Udotea — U. minima Ernst — is described, with specially 

 full details as to branching, growth, and manner in which a false rind 

 is formed. Udotea Desfontainii (Lamx.) Dene, is also fully described and 

 especially the regeneration phenomena, which are particularly interesting. 

 All parts of the plant can show regeneration. The phylogeny and 

 systematic classification of the Codiacece are also explained. He also 

 describes the manner in which the branch filaments are so arranged and 

 differentiated as to form in the highest type, Halimeda, a perfectly close 

 " rind " or bark consisting of the ends of filaments without spaces between 

 them. Udotea has not quite so perfect an arrangement, but there is a 

 difference between the central string and the branch filaments. For the 



