CULTURE AND MORPHOLOGY 85- 



The capacity of Acetabularia and Dasycladus to regenerate 

 lost parts has been known for a long time. For this reason these 

 algae provide particularly excellent material for experimental 

 work; and they have been used to good advantage by Hammer- 

 ling and his associates. Hammerling has found that if the termin- 

 al end of Acetabularia is removed from the basal, nucleus-con- 

 taining portion, it will continue to live for loo to 150 days; and 

 if it had not yet formed a disc but was in an advanced stage of 

 development, it would produce a complete disc at the distal end 

 and at times one at the opposite end also. Neither of these discs 

 would attain the maximal size characteristic of the species, how- 

 ever, and in the absence of nuclei no cysts are produced in the 

 chambers of the discs. 



It is of great importance to note that discs that are intermedi- 

 ate in the characters of two species are produced by grafts be- 

 tween parts of two species each of which contains a nucleus, or 

 between parts of two species only one of which contains a nu- 

 cleus, or between parts of two species neither of which contains 

 a nucleus. 



From these and other experiments Hammerling concludes 

 that the nucleus produces form-building substances or their pre- 

 cursors which function in the ontogenetic development of the 

 plant. It is apparent, furthermore, that these substances are 

 formed in advance of the time that their role in ontogeny be- 

 comes apparent. 



Brief consideration is given below to a few of the innumerable 

 problems in the morphology and taxonomy of the green algae 

 that especially call for a study of plants grown in culture in addi- 

 tion to specimens obtained from the sea. 



Some of the genera and many of the species representative of 

 the orders Volvocales and Chlorococcales and the family Chaeto- 

 phoraceae of the Ulotrichales are based upon very insecure foun- 

 dations. Kylin (1935) and more recently Mrs. L. Moewus (1949) 

 cultured a few of these algae and were thus able to determine the 

 limits of the species in a much more satifactory way than hereto- 

 fore had been possible. It would seem that many more of these 

 algae could be similarly studied to great advantage. The excellent 



