1915 Fallisj on Xereocystis 3 



The effect upon growth of cutting the frond tips shorter and shorter 

 is shown in Table 2. The table shows an average of about ten plants 

 of each different leaf length experimented upon. Healthy kelps were 

 selected and the fronds cut to a length of three feet. These increased in 

 twelve days to an average of five feet in length with a rate of growth of 

 two inches each day. Those cut two feet long grew in twenty-two days 

 to be five feet and a half inch long, with an average daily rate of growth 

 of one and three fourths inches. Some of those cut to twelve inches long 

 grew in twenty-three days to be fifty-three inches in length, and had an 

 average daily growth of one and sixty-two hundredths inches. The six- 

 inch frond grew to an average length of thirty-one and eighty-three 

 hundredths inches in twenty-three days, with an average daily growth of 

 one and thirteen hundredths inches. A later measurement of one of the 

 six-inch fronds was made on Aug. 1. and in spite of the frayed end, the 

 frond measured sixty-seven and a half inches, showing a growth in that 

 one frond from a leng-th of six inches to that of five feet seven and a half 

 inches in thirty-four days.. Only in young plants did growth take place 

 when the fronds were cut to within an inch of the bulb. These grew to 

 an average length of three and one-fourth inches in twenty-three days, 

 and grew nearly one tenth of an inch daily. In no case was growth found 

 to occur in the lower, firmer, more rounded portion of the frond below 

 the flattened expanded part. Therefore no record is given in the table 

 of the larger plants in which this basal part was more than an inch long. 

 Only in the younger plants was there any growth to record for the first 

 inch. No perceptible growth was found to occur in this stalked part in 

 any of the observations, even though the rest of the frond was not re- 

 moved. The shrinkage in the last column of Table 2 seemed to be due to 

 loss of turgidity. A very slow growth, too slow to measure under the 

 conditions, must take place there as in the bulb, since in old kelps the 

 rounded bladeless basal part of the fronds is slightly longer than in the 

 younger ones. If rapid growth did take ])lace here, we would find these 

 stalks much elongated, whieli is never the case. 



I'rom Table 2, we note the different rates of growtli and the in- 

 crease in rate with the increase in length of the frond. This clearly 

 shows that growth extends for some distance up from the base. Setchell 

 (4) says: "All kel))s have physiological regeneration of the blade to a 

 greater or less degree. The blade disintegrates and is worn away above 

 and is renewed at the base at the same time that the sti})e is increasing 

 in length at the u])p( r end. This process is continuous during the season 

 of growth." This is all true, but there is a question eoueeruiiig how nuieh 

 of the frond may be considered as base. 



