LIFE HISTORIES OF ALG^ 237 



and other marine animals. In 1913 it was successfully 

 accomplished by Overton with the eggs of Fucus. The 

 eggs were dipped for about a minute, or a minute and a 

 half to two minutes, in a mixture of 50 cc. of sea-water 

 plus 3 cc. of a very weak solution of acetic, butyric, or 

 other fatty acid, and then transferred to normal sea- 

 water. This treatment caused the formation of the fertili- 

 zation-membrane, quite as in natural fertihzation by the 

 sperm. If, after the formation of the membrane, the eggs 

 are placed for 30 minutes in hypertonic sea-water (50 cc. 

 of normal sea-water plus 8 to 10 cc. of a weak solution of 

 sodium chloride (common salt), or potassium chloride), 

 and then back into normal sea-water, the eggs begin to 

 divide and continue to develop into young plants. The 

 question as to the chromosome number in the cells of 

 plants formed by artificial fertilization is of very great 

 interest, but has not yet been investigated. 



218. Gennination of the Oosperm. — After either natural 

 or artificial fertilization the young zygote begins at once 

 to divide, without any period of rest. Of the two cells 

 formed by the first division, one gives rise to the hold-fast 

 organ, by which the new plant is attached to the rocks, 

 while the other develops into the main body of the plant, 

 which resembles the parent plant in all external characters 

 (Fig. 175). 



219. Reduction. — As always in normal fertihzation, the 

 nucleus of the oosperm is diploid, and the Ascophyllum 

 plant that develops from it is also diploid. It is therefore 

 the sporophytic generation. At the end of the first two 

 nuclear divisions of the spermagonia and oogonia, re- 

 duction has been accoihplished, and the four nuclei that 

 result are haploid. They therefore belong to the haploid 



