556 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Frond of Polysiphonia.* — Herr L. K. Eosenvinge contests the 

 theory of Schwendener that the spiral arrangement of the " leaves " of 

 Polysiphonia is brought about by contact of these organs with the axis 

 which bears them. In P. violacea he found no such contact, even at the 

 earliest period. The " leaves " of the lateral shoots of many species of 

 Polysiplionia are from the first arranged in a regular sinistrodromal 

 spiral not resulting from any contact. 



The cells of many Florideae are united by pores formed apparently 

 at the same time as the walls which they perforate. In several species of 

 FolysipJionia, especially in P. violacea, the author finds in addition, and 

 in the pericentral cells, " secondary pores " formed in a very remarkable 

 way. The young cell contains a rather large nucleus, which soon 

 divides into two, the lower of which lies on the lower and outer 

 angle of the cell. A small triangular piece of the cell containing this 

 nucleus is now cut off by an oblique wall, and this segment passes 

 through the underlying wall, and coalesces with the subjacent cell. Its 

 nucleus passes into the underlying cell, but a fine strand of protoplasm 

 remains uniting it with the protoplasm of the cell from which it was cut 

 off; and the pores through which these strands pass are the secondary 

 pores. The author compares this process with a similar one in the 

 Hymenomycetes. 



Apical cell of Lomentaria and Champia.t — According to Prof. N. 

 Wille there is in Lomentaria Jcaliformis only a single aj^ical cell, from 

 which segments are cut off in different directions. This is to some 

 extent at variance with the observations of Debray and others4 The 

 branches are hollow with transverse diaphragms. The outer wall con- 

 sists only of two primary layers, the outer of which afterwards gives rise 

 to the small cells filled with endochrome. In older branches these cells 

 expand into a connected layer outside the outermost primary layer. 

 The inner of tbe two primary layers constitutes a conducting system ; 

 but the cells of this system originate by tangential division of young 

 cells of the outer layer. In the centre of the apex is a large cell which 

 has probably been formed from the apical cell of the outer layer by a 

 division parallel to its base. This apical cell is polygonal, and from it 

 are separated daughter-cells in six directions. 



Prof. J. G. Agardh § agrees generally with the view of Wille that 

 the cells of the outer layer in the frond of Lomentaria and Champia 

 originate from the outer cells of the inner layers. These internal layers 

 put out outwardly ramifications which form the outer parenchyme of the 

 thallus, and inwardly ramiScations which form the diaphragms. 



Bulb of Laminaria biilbosa.|| — Mr. C A. Barber has investigated 

 the structure of the stem of this sea-weed, which differs from that of 

 other species of the genus. It is characterized by the peculiar bulb-like 

 enlargement of the base which is attached to the substratum by several 

 successive circular rows of " hapteres," and by its bearing sporanges on 

 the '' bulb." While in other species of Laminaria the hapteres arise as 



* Bot. Tidskr , xvii. (1888) pp. 1-19 (1 pi.)- See Bot. Centralbl., xxviii. (1889) 

 pp. 528, 529. 



t Bot. Notiser, 1887, p. 252. See Bot. Centralbl., xxxvii. (18S9) p. 420. 



t Cf. tills Journal, 1888, p. 265. 



& Ofv. K. Vetensk Akad. Forliandl., 1888, pp. 49-68. 



\\ Ann. of Bot., iii. (1889) pp. 41-64 (2 pis.). 



