48 Vol. XLnr., Art. 1.-K. Yendo: 



splitting is admitted to have taken place (cfr. p. 11). Yet there 

 is no doubt that the principal growth of the fronds, in length and 

 in breadth, of the Laminariaceous algae results from the activity of 

 the transition region, where the meristematic tissues are located. 



Soon after the precortical layers make their appearance in the 

 transition region, the embryonal fronds of Alaria begin to reveal 

 some of the generic peculiarities in a primitive state, /. e.\ 1), the 

 mucilage glands frosted about the boundary between the monostro- 

 matic and the polystromatic area : 2), formation of the midrib. 

 These two peculiarities can be perceived when a frond has attained 

 the total length of C-7 mm. In this respect the embryonal fronds 

 of Alaria resemble those of Undarla most. Both are, however, 

 distinguishable by the difference of germinating seasons, formation 

 of the pinnules at the transition point and by the localities of the 

 species. The embryonal fronds of Undaria appear early in January 

 in northern Japan, and earlier in middle and southern, while those 

 of Alaria are found in March-May. In Undaria the formation of the 

 pinnules takes place at the transition region soon after the blade 

 has grown to the length of 2 cm. or so. Species of Alaria are 

 limited to the eastern coasts of northern Japan while Undaria is 

 limited to the west coast of the Hokkaido and to both sides of the 

 Main Island. But in the vicinity about the Tsugaru Strait, where 

 Undaria pinnatifida and A. crassifolia occur living together, separation 

 of the plants by the last meritioned point is of course unreliable. 

 The appearance of the sporophylls takes place in most species 

 n June-July, varying according to the germinating time of the 

 sporophyte frond. The first few sporophylls remain less developed 

 in size when compared with the successive upper ones (Plate IX, 

 fig. 1). New sporophylls come out continuously upwards on both 

 edges of the stipe till the later part of spring. Those sporophylls 



