240 SUMMARY OF CURRENT RESEARCHES RELATING TO 



its pale frond. Certain of the stipites, which were broken off and bad 

 no haptera, exceeded 1 m. in length and had a basal diameter of 

 3-3 '5 cm. The stipes is greyish-brown, quite smooth, very slippery, 

 very flexible, without epiphytes, and contains muciferous canals arranged 

 in two distinct rows in the young portion, one at the interior limit of 

 the outer layer {korce), the other outside the first and losing its 

 distinct character in older portions of the stipes. At the base the 

 intermediate layer of cells between the medulla and the outer cells 

 comprises two concentric zones. The medulla, round or elliptic, 

 sometimes slightly excentric, retracts sharply when exposed to the air 

 and becomes white, like elder-pith. The whole decays rapidly in the 

 air. All these characters are entirely opposed to those of L. Gloustonii 

 with its rigid consistency. The outer layer of both species is rich in 

 fucosan, fairly evenly distributed. In contrast to L.flexicanUs, the 

 stipes is neither enlarged nor diminished at its extremity, and the 

 cordiform base of the lamina widens suddenly ; also it differs from 

 L. flexicaulis in the outline of the medulla. The lamina of L. Lejolisii, 

 about 1 m. long, provided with muciferous canals, is more transparent 

 than those of other species of Laminaria ; it is whitish, particularly at 

 its undivided base. The segments, longer- and less coriaceous than 

 those of L. Gloustonii, bear large irregular sori corresponding more or 

 less on both surfaces, and often partially destroyed by Helcion pellucidum. 

 L. Lejolisii was found in three places growing with L. Gloustonii, and is 

 certainly a new record for France. It is not a hybrid of L. Gloustonii 

 and L. flexicaulis, but a distinct species, and approaches most nearly in 

 exterior appearance to L. pallida Grev. That species is, however, 

 incompletely known, and it is possible that the name has been applied 

 to three distinct species, all of them different from the Roscoff plant. 

 The appearance of L. Lejolisii at Roscoff is of recent occurrence and is 

 a parallel case to that of Golpomenia sinuosa. If the deductions of 

 Le Jolis relative to the concentric zones of L. Gloustonii are accurate, 

 and if they apply to L. Lejolisii, the specimens collected would be two 

 years old. The species can be propagated by zoospores, for the author 

 has some growing under culture. It has also spread and multiphed at 

 Roscoff. It was probably introduced by a ship or submarine and 

 appears to be flourishing, in which it forms a contrast to Alaria esculenta, 

 which after a whole century of existence on the French coast does not 

 spread. The author points out that if the invasion of L. Lejolisii 

 continues it will oust L. Gloustonii, which is very rich in iodine, but 

 has less rapid growth. 



Alternation of Generations in Laminaria digitata.* — H. Kylin 

 publishes an account of his investigations on the germination of the 

 zoospores of Laminaria digitata and the development of the young 

 stages of the plant. These agree with the published researches of 

 Sauvageau on the same alga. He describes his methods of culture, 

 the germination of the zoospores, the male gametophyte, the female 

 gametophyte, and the sporophyte, and gives figures of stages in their 

 development. 



* Svensk Bot. Tidskrift, x. (1916) pp. 551-61 (figs, in text). 



