A Monograph of tlie Genas Alarla. 51 



BÖRGESEN : Note on the question whether A. cscutenta 



sheds its Lamina periodically or not. 1904. 

 Oltmanns : Morph, 'und Physiol, der Algen. 1904. 



In various herbaria in Europe which I have visited, there was 

 no specimen of Alarla to give any evidence in support of the view 

 that the plant is perennial and sheds the blade periodically. I 

 have seen a single specimen with a constriction in the blade in 

 the Herbarium of Trinity College, Dublin. The specimen was col- 

 lected by NoLT and sent from Sonder under Laminaria Noliil Ag. 

 At the constricted point the blade becomes quite narrow, measur- 

 ino- but a few millimeters on both sides of the midrib. From this 

 point the blade expands to its normal breadth, more or less 

 abruptly upwards and comparatively gradually downwards. The 

 substance of the blade in the two parts has no marked difference, 

 therefore not justifying the view regarding the upper part as hav- 

 ing grown at quite a different season from the lower. The midrib 

 is in substance, thickness and breadth uniform throughout the 

 whole length. The statement made by Haevey in Phyc. Brit., 

 Plate 79, about the regular change of the blade of A. esculenta, 

 however, seems not to have been derived from this specimen. 



PiOSENVENGE^) givcs pliotographs of two specimens of Alarla 

 from Greenland, each with a remnant of the old blade at the top 

 of the new. Thoy may be taken as full proofs of the renewal of 

 the blade of Alarla but not of the perennial existence of the plant. 



On the coasts of Japan, most Alarla attain their full maturity 

 in summer. The species which inhabit the comparatively warmer 

 waters, such as A. crasslfolla and A. prcelonga, discharge the 

 spores during July- August with the utmost vigor ; and the fronds 

 are entirely washed away from the substrata before the end of 



1) RosENVENGE : On the Mar. Alg. from N.-E. Greenland, p. 113, fig 5. 



