REVIEWS. 
137 
heads. The appearance was not gradual so far as any outward indica¬ 
tions show. It was an abrupt leap. Whether the mutation took place 
four years back in the first generation, and laid dormant for four years, 
or whether it developed gradually through the four generations, suddenly 
to appear in the fourth, or whether the entire change was accomplished 
in the individual, where it was first manifest, it is difficult to say. The 
experiment was begun in 1896 and in 1901 the number of rays had in¬ 
creased from 21 to the maximum of 200, or to complete doubling. 
The race is constant and no atavists or reversionists have appeared 
since the first purification of the race, though fluctuating variability occurs. 
The new variety is termed plenum. All the offspring of the parent that 
first showed the mutation manifested the new character with but a single 
exception in any blossom, and deVries thinks the inner change thus 
manifest took place within the plant of the fourth generation. 
SUMMER COURSES IN BOTANY. 
For the benefit of teachers who are contemplating summer study, we 
give below a list of courses offered at various institutions during the com¬ 
ing summer, announcements of which have been received. 
The University of Chicago. First Term, June 17 to July 27. Second 
Term, July 28 to September 1. 
Staff : Professor John M. Coulter, Assistant Professor B. M. Davis, 
Dr. Charles J. Chamberlain, Dr. H. C. Cowles, Dr. W. J. G. Land, Dr. 
W. B. McCallum, Dr. E. N. Transeau, Dr. F. M. Lyon, Miss Tarrant. 
Courses: Advanced Morphology, Professor Coulter, Dr. Chamberlain. 
Research in Morphology, Professor Coulter, Dr. Chamberlain. Special 
Morphology of Angiosperms, Professor Coulter, Dr. Chamberlain. Gen¬ 
eral Morphology of Spermatophytes, Professor Coulter, Dr. Land. Spe¬ 
cial Morphology of Algae, Assistant Professor Davis. Cytology, Dr. 
Chamberlain. Field Ecology, Dr. Cowles, Elementary Botany, Dr. Lyon. 
General Morphology of Bryophytes and Pteridophytes, Dr. Lyon. Meth¬ 
ods in Plant Histology, Dr. Land. Field Botany, Dr. Land, Miss Tar¬ 
rant. Elementary Plant Physiology, Dr. McCallum. Elementary Ecol¬ 
ogy, Dr. Transeau. 
Cornell University. July 5 to August 16. 
Staff: Assistant Professor W. N. Rowlee, Dr. E. J. Durand, Miss E. 
M. Cipperly. 
Courses : Elementary Plant Physiology and Morphology, Dr. Durand, 
Miss Cipperly. Special Morphology and Ecology of the Higher Plants, 
Assistant Professor Rowlee, Miss Cipperly. Taxonomy and Embryology, 
Dr. Durand. Trees and Shrubs, Assistant Professor Rowlee. 
Harvard University. July 5 to August 15. 
Staff : Dr. Robert Greenleaf Leavitt, Director of Summer Courses in 
Botany; Mr. Amon B. Plowman, Mr. J. R. Johnston. 
