138 Puget Sound Marine Sta. Pub. Vol,. 1, No. 13 



Laminaria 5, 10, 20, 40, and 60 cm. long were located in their natural 

 habitat and marked. Three plants of each species were selected of each 

 length. Their growth was compared with the growth of the same nmn- 

 ber, kind and length of plants artificially attached to a raft. The figures 

 thus secured of the growth in length of the 15 naturally attached Costaria 

 plants showed an average daily increase of 1.261 cm., while 15 plants 

 artificially attached to the raft showed 1.226 cm. The average daily in- 

 crease of the 15 naturally attached Laviinaria plants was 1.08 cm., while 

 that of the 15 artificially attached to the raft was 1.09i cm. No more vari- 

 ation was shown between those naturally and artificially attached than 

 between different plants of either group. The averages in each case show 

 a slight increase in the plants attached to the raft over those naturally 

 attached. Therefore, for the convenience of the experimenter, a raft 

 about 5x14 feet was constructed of logs with boards on top. The plants 

 were tied by means of cloth strings to staples driven into the logs on the 

 sides. Each individual ^jlant was numbered on the raft near the staple. 

 In a great many cases small stones aided in submerging the plants to any 

 desired depth by varying the length of the strings. A record of the growth 

 of the plants was kept between June 15th and August 6th. The measur- 

 ing was done with a celluloid millimeter ruler. The plants were marked 

 with slight, straight cuts or scratches made with the point of a knife down 

 the center of the blade, or on the midrib of those species which possess 

 one. As the blades grew, the marks also broadened and lengthened, but 

 could easily be discerned from scars made by Lacunae or other animal 

 pests of attachment; except in those plants experimented with to see what 

 effect the removal would have, and others from which they had been torn 

 accidentally in the course of the experiments. The tables given in this 

 paper represent not the growth of a single plant, but the average of several 

 plants. 



Comparing the results obtained from the growth of plants from which 

 the holdfasts and a large part of the stipes were removed with those from 

 which the holdfasts had not been removed, shows that the plants grow as 

 well without tlie holdfasts or even a large part of the stipes as with them. 

 The average daily increase in length of several Costaria plants with the 

 holdfast present was 1.5 cm.; others w^ithout the holdfast, 1.4 cm. The 

 average daily increase in length of several Alaria plants with the holdfast 

 present was 2.01 cm.; of others of about the same length without the hold- 

 fast, 2.04 cm. The same indifference to holdfasts obtains in the other 

 genera of plants experimented with, although the figures are not given. 



The effect of removing the tips of the blades proved to be equally 

 negligible. Plants of the same approximate size grew nearly at the same 

 rate even tho the tips of some were removed. Mature plants, however, 



