POTASH FROM KELP. 7 
embryos excepting in midwinter. Observations on the rate of 
growth of embryonic plants indicate that they may readily attain 
sufficient size to be visible to the unaided eye within six weeks after 
appearing as embryos. Thus it may be stated that, under favorable 
conditions, the pre-embryonic or sexual stage requires six weeks, 
and the microscopic portion of the embryonic stage requires about 
six weeks, making a total of about three months from the germina- 
tion of the spore to the appearance of the visible plant. 
LATER STAGES. 
The postembryonic development of the plant has been worked out 
from observations of plants in kelp beds, on beaches, and on the 
breakwater at San Pedro. The last place has proved to be of especial 
service in these investigations, and we wish here to express our 
appreciation to Dr. N. S. Gardner, of the University of California, 
_ for suggesting the use of it. 
Enough young plants were here observed to enable one to piece 
- out the course of development by comparing them with the young 
_ plants that came up in the spring. All kelp and other large sea- 
_ weeds, except such plants of Macrocystis as were reserved for study, 
were removed from small areas of the rock surfaces of the break- 
water. Some of the mud with small plant and animal forms was 
- scraped from the ‘rocks for examination under the microscope. 
Young plants down to 3 or 4 inches in length were found in very 
small numbers in November. For three or four months some of these 
seemed to wear away nearly as fast as they grew, while others dis- 
appeared. Finally, in February, all the small plants originally se- 
lected were gone and only three new plants had been discovered. 
These plants were all about 16 to 18 inches tall. Examination of 
scrapings collected in November and December revealed small em- 
bryonic plants resembling Egregia in color rather than Macrocystis. 
Not until in February was an embryonic plant found that appeared 
to be Macrocystis. This oecurrence was contemporary with the 
appearance of embryos in the laboratory culture. At this time 
young Egregia plants half an inch to over a foot high could be 
seen in small numbers here and there. Later on, in March, the 
young Egregia plants were becoming quite abundant, but no new 
plants of Macrosystis were as yet large enough for identification. 
All old plants had disappeared over considerable areas. No obser- 
vations were made in April because of insufficiently low tides. 
When the breakwater was again visited, early in May, great 
changes had taken place. In all the crevices, pockets, and other 
more or less sheltered places among the rocks dense clumps of 
Egregia plants up to 2 feet high were growing. Plants of Macro- 
cystis from 1 to 18 inches high could be found among these others. 
When visited again, the last of May, Macrocystis plants that had 
measured 10 to 13 inches in height early in the month were 2 or 
more feet high. All these vigorous young plants were on rocks that 
were bare in February and still nearly bare in March. From the 
_ evidence furnished by examination of the rocks, microscopic ex- 
_ amination of scrapings from the rocks, and experimental cultiva- 
tion of spores in the laboratory, it seems that young plants of Macro- 
cystis, some of them 18 inches high, had grown from spores ger- 
