1916 Fallis; on Laminnriaceae 145 



at 5:30 o'clock, night and morning, on Nereocystis, Laminaria, Costaria, 

 Alaria, and Agaruni. Observations were made on several plants of each 

 genus. The results are given in table 4. 



SUMMARY 



1. Kelps will grow suspended from a raft as well as in their natural 

 habitat. 



2. The holdfast and stipe are not necessary for the growth of the 

 blades ; holdfasts merely serve to anchor the plants ; stipes hold the blades 

 in the proper position for growth. 



3. Cutting off the tips of blades does not stop their growth. The 

 larger plants grow faster than the smaller, 



4. Summer growth in the stipes of kelps, with the exception of 

 Nereocystis, is very slow. 



5. Growth in the stipes occurs in that part nearest the blade. 



6. Blades of the various kelps may be cut into squares as small as I 

 mm. and each piece still grow independently. 



7. Blades of kelps grow in width when cut into narrow strips. 



8. The whip-like midrib of Alaria will grow in length when the 

 thin part of the blade is removed from it. 



9. The basal limit of growth of all the kelps named in this paper, 

 with the exception of Nereocystis, is close to the transition point between 

 blade and stipe. 



10. The greatest growth occurs not at the transition point between 

 blade and stipe, but near the base of the blade. This is usually 3-10 cm. 

 from the base, depending upon the age and form of the plant. 



1 1 . The greatest growth in length usually occurs in the general 

 region of greatest width. 



12. The rate of growth increases rapidly for a short distance from 

 the base, and then decreases more slowly toward the tips of the blades, at 

 which point no growth occurs in an ordinary July plant. 



13. The sijorophylls in Alaria grow at rather a rapid rate, decreas- 

 ing as the stage of maturity is reached. 



14. Kelps grow more in the day time than at night, the rate of 

 growth during the day being almost double that at night. 



