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1906] YAMANOUCHI—POLYSIPHONIA VIOLACEA 403 
germinating tetraspores and carpospores and in the vegetative cells 
of mature plants; then comes an account of spermatogenesis, forma- 
tion of procarp, fertilization, and development of the cystocarp; 
tetraspore formation is then considered, followed’ by a description of 
certain abnormalities; finally, there is a discussion of the cytological 
phenomena and alternation of generations. This last topic has been 
given considerable attention, for the chief results of this investigation 
have been the establishment of an antithetic alternation of generations 
in Polysiphonia, with the period of chromosome reduction at the 
time of tetraspore formation. 
The investigation was begun during the summer of 1905 at the 
suggestion of Dr. BrapLey M. Davis during my stay as an occupant 
of a Carnegie research table at the Marine Biological Laboratory, 
Woods Hole; and to the Carnegie Institution I wish to express my 
obligations for the privilege of the table. The studies were con- 
tinued and completed by me in the Hull Botanical Laboratory as a 
Fellow of The University of Chicago, under the direction of Professor 
Joun M. Courter and Dr. Cuartes J. CHAMBERLAIN, the kind 
assistance and painstaking criticism of Dr. Davis continuing also 
throughout the whole progress of the investigation. To these gentle- 
men I am under great obligation; and also to the other members of 
the botanical staff of Hull Botanical Laboratory for courtesies extended 
to me in many ways. 
THE FIRST MITOSIS IN THE GERMINATING TETRASPORE. 
The tetraspore when discharged from the parent plant assumes 
a spherical form. Plastids usually lie near the periphery of the cell, 
Whose cytoplasm presents an irregular, coarse alveolar structure, with 
the nucleus lying near the center. The cytoplasm surrounding the 
nuclear membrane is a finer network than anywhere else in the cell. 
Within the nucleus there is a very delicate linin mesh dotted here and 
there with chromatic granules (fig. 1). From the fact that the trans- 
vetse walls of the cytoplasmic alveoli end on the nuclear membrane at 
points where the linin threads start, it seems possible that there exists 
a close physiological relation between these structures. The nucleus 
8enerally contains a single nucleolus, variously situated and homo- 
8eneous in structure, but sometimes two nucleoli are present. 
