A Monograph of the Genus Alwin. gft 



glands gain their size by expanding in all directions, hence the 

 epidermal cells have to be arranged radially at an early stage of 

 development of the glands.^) This difference may be easily ex- 

 plained from the modes of growth in the two plants. In Undaria, 

 the pinnae extend in area by the growths in length and w^idth, 

 but in Alaria, the embryonal blade grows much quicker in length 

 than in w^idth. 



I'^) have already mentioned the difference in number of the 

 glands in the marginal and the middle part of the frond of Undaria. 

 In the former part there are always more numerous glands than 

 in the latter. In Alaria crassifolia, the glands arc practically 

 limited to the margins of the blade (Plate XVIII, fig. 8). 



When the fronds of A. crassifolia have attained the length 

 of 50-G0 cm. and the sporophylls make their appearance as small 

 ligules, there are very few glands, if any, to bo found in the 

 transition region or in any other part of the blade. But in the 

 membranous sterile part of the sporophylls, which are to be found 

 in a further advanced stage of frond, the mucilage glands are very 

 well developed. 



In A. ßstidosa, the largest form among the genus, the glands 

 may be seen all over the blade, except the midrib, even after the 

 numerous sporophylls have appeared.^) The glands of this species 

 are not stretched longitudinally as in A. crassifolia ; those in the 

 transition region are nearly as round as those of Undaria, and 

 those in the part about a meter or so above the transition point 



1) Yesdo : On Mucilage Glands of Undaria, Plate XLVIU, fig. 7. 



2) ritto, p. 614. 



3) Miss KiBBK observes a peculiar sort of cells in the frond of Abiri i fisbdosa and re- 

 gards them as a fungus. I am inclined to doubt her observation ; she may have mistaken the 

 glandular cells as a parasite. (Riget Sound Marine Station Publication, Vol. I, No. 20 1916). In 

 her previous paper (the same PubUcation, Vol. I, Xo. 8. 1915) specially treating on the struc- 

 ture of Ahiua fistulosa she gives no account on the remarkable glands. 



