140 Piicjet Sound Marine Sta. Pub. Vol. 1, No. 13 



blade (table 1). In most plants no growth was found in it; in others, and 

 especially in the younger plants, a slight increase in length was observed. 

 However, most of the growth of the stipe occurs in that part nearest the 

 blade. In some of the records the greater increase in the length of the 

 upper centimeter of stipe may have been due in part to the inclusion of a 

 portion of the blade, since the transition point is often not clearly marked. 

 The growth of the stipe evidently occurs mostly during the young stages, 

 so that little elongation takes place after the blades are well under way. 

 Considerable growth takes place at the transition point between blade 

 and stipe, so that the blade appeared to be growing backward from the 

 first mark made at its base (Fig. 2). This growth at the transition point 

 was noted in all the Alaria, Laminaria, and Egregia plants, though it was 

 not so marked in Costaria, Agarum, and Cymathere. This may be due to 

 the fact that in the three last named genera there is a more abrupt passage 

 from stipe to blade, thus the boundary could be more accurately located; 

 while in the three first named the more gradual merging of stipe into blade 

 made it difficult to know where to place the boundary mark. Thus what ap- 

 peared to be a backward growth of the blade (Figs. 2, 4, 6) may have 

 been the increase in length of a very short basal portion of the blade con- 

 sidered as a part of the stipe. 



The growth in width of the blade was an object of experiment in 

 Costaria, Laminaria, Alaria, and Agarum. Yendo (6) says that when a 

 young Costaria plant has developed the five ribs it begins to increase its 

 length at a considerable speed, the increase in breadth not remaining pro- 

 portional to the increase in length. He thus finds that at the beginning 

 of summer the growth in length seems practically to have ceased in the 

 blades, while the increase in breadth continues and causes remarkably 

 wide plants. The writer has data for the summer months only; but these 

 show more rapid growth in length than in width of the blade. 



Various methods of locating the region of greatest growth in width 

 were tried. All showed the same general result. One of these methods was 

 to cut a longitudinal strip from the central region of a blade and observe 

 where the greatest enlargement in width took place. The results by this 

 method lend themselves well to graphic representation (Figs. 7, 8; 9, 10; 

 11, 12; 13, 14). This region is surprisingly near the base in all the blade; 

 and it practically coincides with the region of most rapid elongation. In 

 those plants having a midrib it is necessary to leave a small strip of the 

 thin portion of the blade on the midrib, altho this may be very little. The 

 rib alone will not grow a new blade so far as the writer's observations 

 went. However, pieces of blade as small as 1 mm. square will grow in 

 width (table 2). 



