1916 



Fallisj on Laminariaceae 



141 



Table 2. Showing ten days growth of small pieces of blades. 



Original Size 



Size 10th Day 



Length 



Width 



Lengtli 



Nereocystis 



cm. 

 .1 

 .5 

 .1 

 .5 

 .5 



cm. 

 .1 



.5 

 4.8 

 4.5 

 1.0 



cm. 



.16 



.6 



.2 

 1.1 



.65 



cm. 



.15 

 .57 

 5.1 

 4.8 

 1.2 



Alaria 



10 



5 



.1 

 .5 



3.1 



3.1 



1 



1 



1 



.15 



.75 



.3 



2.0 



.7 



16.2 



10.1 



.15 



.6 

 4.2 

 4.4 

 1.5 

 2.4 

 2.2 



In general during the summer season the larger plants grow more 

 rapidly than the smaller ones, as might be expected from the usual ex- 

 perience with higher plants. Considering the large as well as the small 

 plants experimented with, the average daily rate of growth in width at 

 the most rapidly widening point was in Costaria 4.3 mm., in Laminaria 

 1 mm., in Alaria 2.8 mm., in Agarum 2.3 mm. No good data for rate of 

 growth in width were secured for Cymathere and Egregia, but their growth 

 is much larger. 



Experiments were made to determine both the region and the rate 

 of elongation. The basal limit of elongation is near the transition point 

 between stipe and blade. Egregia, whose blades grade gradually into the 

 stipes, shows more growth in the stipe than do those species in which the 

 transition is abrupt. The region of greatest growth is from 2 to 20 cm. 

 from the bast of the blade in the kelps experimented with {Figs. 8, 4; 

 5, 6) ; on the average it is greatest between 3 and 7 cm. from the base, 

 depending upon the age and the form of the blade. In all the plants ob- 

 served the growth was greatest in the general region of greatest width 

 {Figs. 15, 16). If the blade broadens gradually, the region of greatest 

 growth is farther from the base than if the blade broadens abruptly {Figs. 

 15, 16). In larger and older plants the growth continues for a greater 

 length, but the proportion of growing blade is about the same as in the 

 younger plants. In no case was there any perceptible growth found near 

 the tip of the blade. Yendo (6) says that "the growth in length, as well 

 as in breadth is due at a certain period, to both apical and the stipo-frondal 

 growth. The apical growth is gradually retarded, and finally ceases. 



