SOME NUCLEAR CHANGES ACCOMPANYING DEVELOPMENT IN THE ENDOSPERM OF GLEDITSIA AND PODOPHYLLUM

The development of the endosperm in Gleditsia is marked by the growth of the average nucleus from 141 μ³ on June 12 to 978 μ³ on July 14. At the time of formation of a cellular endosperm the average nuclear volume commences dropping and by July 20 reaches an average of 224 μ³ throughout the endosperm. In Podophyllum at the time of cell formation the average nuclear volume begins to drop from a value of about 2850 μ³ and falls to a value of from 500 μ³ to 770 μ³, the latter estimates depending upon the mode of fixation of the material. The volume decrease in the Podophyllum endosperm nucleus is accompanied by a fall in mean relative DNA content of the average nucleus, as determined by microspectrophotometry with the two wavelength method. The possibility of degeneration of some of the higher “ploid” types is considered, as well as depolyploidization.