426 



SCIENCE. 



[N. S. Vol. XXIII. No. 585. 



possible upon the working' of the option. 

 The only serious criticism that has devel- 

 oped has been with reference to the number 

 of topics, which has been found by most 

 teachers to be too great for the time the 

 option is supposed to take (one year). The 

 committee accordingly recommended the 

 omission of certain minor topics which will 

 render it about one tenth shorter than at 

 present, and improvements in certain minor 

 details. These changes will soon be pub- 

 lished in the Plant World, and will be laid 

 before the college entrance examination 

 board. The committee also called attention 

 to the fact that although many schools now 

 offer this full-year course in botany, com- 

 paratively few students take the college 

 entrance board examination in that subject. 

 This is obviously due to the fact that few 

 colleges as yet include a year course of 

 botany among their entrance options, and 

 this, no doubt, largely because the existence 

 of a definite highly-graded course in that 

 subject has not yet been brought officially 

 to the attention of the authorities. The 

 recommendation was made by the committee 

 that the members of the society who are 

 teachers should at least make sure that the 

 matter is not going by default in their own 

 institutions. 



The Formation of Tetraspores in Grif- 

 fithsia: Professor D. S. Johnson and 

 Mr. I. F. Lewis, Johns Hopkins Uni- 

 versity. 



The tetrasporangia are borne in whorls 

 at the junction of two cells of the thallus. 

 Each tetrasporangium rudiment arises as 

 a papilla-like outgrowth from the apical 

 region of the cell of the thallus. By a 

 horizontal division this outgrowth gives 

 rise to two cells, a basal stalk cell and a 

 terminal tetrasporangium. The tetraspo- 

 rangia! cell increases in size and the nu- 

 cleus divides into two, then into four, the 

 nuclei lying peripherally in the cell. The 



nuclei then travel toward the center of the 

 cell, and simultaneously partitions grow in 

 from the periphery. The four nuclei lie in 

 a central mass of rather dense cytoplasm, 

 the partitions just reaching the outer bor- 

 der of the central mass. In this condition 

 the tetrasporangium is shed, the actual 

 separation of spores taking place in the 

 water. 



TJie Curly Top or Western Blight of the 

 Sugar Beet: Dr. C. 0. Townsend, United 

 States Department of Agriculture. 

 This paper consisted of a discussion of 

 twenty-three theories that have been in- 

 vestigated during the past five years, rela- 

 tive to the cause of the curly top or western 

 blight of the sugar beet. The theories dis- 

 cussed included parasites, unfavorable soil, 

 climatic and cultural conditions, inherent 

 tendencies in the plant toward the disease, 

 and a weakened condition of the plant due 

 .to poor seed. None of the theories investi- 

 gated gave positive results in regard to the 

 cause of the disease under the conditions 

 in which the experiments were conducted. 

 The bacterial theory has probably received 

 more attention than any other possible 

 cause of this disease, but the results thus 

 far indicate that none of the organisms 

 isolated are the sole cause of curly top. In 

 some localities the disease is accompanied 

 by insects so persistently that at first sight 

 they seem to be the cause of the trouble, 

 but their almost total absence from other 

 badly diseased fields throws considerable 

 doubt on this theory. The fact that a 

 parasitic fungus was found in the tissues 

 of the roots in several microscopic sections 

 cut from diseased plants, points to this 

 theory as one that needs further investiga- 

 tion. However, inoculations made with 

 this fungus in healthy plants in the field 

 and in the greenhouse have not produced 

 the disease under the conditions employed. 

 It is possible that a combination of un- 



