320 SUMMARY OF CURRENT RESEARCHES RELATING TO 



in favourable conditions, put out branches and initiate a new plant. 

 Very thick-walled hypnospores have been observed in the old balls 

 which had been in a laboratory for eight years ; they burst or cast off 

 the thick wall and put out a long " rliizoid," into which some of their 

 protoplast passes. The origin of the balls is described by Wesenberg- 

 Lund to be as follows : — A shallow part of the lake has its floor clothed 

 with a layer of small tufted separate individuals, which, during the 

 undulations set up by strong winds, hook on to one another and 

 gradually form packets, which again, being rolled by waves and rul)bed 

 against the sandy floor, become rounded, and, losing their apical cells, 

 actively produce lateral branches which bind them together the more 

 firmly. Dying off in the centre, the balls tend to become hollow, and 

 in April and j\Iay contain enough gas within to raise them to the 

 surface. At other times of the year the plankton of the waters provide a 

 screen dense enough to prevent full light from penetrating the waters ; 

 and the balls are unable to rise to the surface. 



Development of the Conceptacle in Fucus.* — M. L. Roe has 



re-investigated the development of the conceptacle in Fucus, and comes 

 to the following conclusions : — 1. The conceptacle originates as a slightly 

 modified continuation of the external layer of the thallus, being segments 

 of the apical cell whose basal portions are constantly meristematic and 

 never entirely breaking down. 2. The hairpit is a juvenile stage of 

 the conceptacle, the sex organs appearing in the same cavity as the 

 mature hairs, but after their loss. 3. A distinct phylogenetic series is 

 seen in advance from continuous patches of hairs and reproductive 

 bodies, to scattered sori, to scattered conceptacles, and finally to apical ly 

 placed conceptacles or to conceptacles on specially developed side 

 branches. All of these structures originate through modification of the 

 superficial layer of the thallus. 



Undaria and its Species. f— Under this title K, Okamura discusses 

 three closely related Japanese species : Undaria pinimtifida Sur., Hirome 

 iindarioides Yendo, and Laminaria Peterseniana Kjellm. He quotes 

 first the original descriptions of each species, adding further details of 

 his own observation. Then he compares each with the other two, and 

 shows that there is an evident gradation from one to the others. Thus 

 by extending the genus Undaria in certain particulars he is able to 

 unite all three species in the one genus. The difference in the sori are 

 shown to be few and relatively subordinate. The chief characters in 

 common are : the winged state of ancipitous stem, the lack of muci- 

 laginous lacunae, the presence of cryptostomata, the characteristic muci- 

 laginous glands, and paraphyses capped with a mucilaginous mass. The 

 extreme forms are U. Peterseniana and U. finnatifida var. distans, and 

 these are connected by U. iindarioides. The affinities and distributioni 

 are discussed. 



* Bot. Gaz., Ixi. (1916) pp. 231-46 (4 pis.). 



t Bot. Mag. Tokyo, xxix. (1915) pp. 266-78 (1 pL), 



