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NEW YOKK 

 UNIVERSITY OF CALIFORNIA PUBLICATIONS ..,.,-.., .^. 



BO 1 ANICAL 



"* OARIJEN 



AGRICULTURAL SCIENCES 



Vol. 2, No. 8, pp. 243-248, plate 44 September 17, 1924 



MICROSPOROGENESIS OF GINKGO BTLOBA L. 



WITH ESPECIAL REFERENCE TO 



THE DISTRIBUTION OF THE 



PLASTIDS AND TO CELL 



WALL FORMATION 



BY 

 MARGARET CAMPBELL MANN 



(Contribution from the Division of Genetics, University of California) 



Microsporogenesis in Ginkgo hiloba L. is especially intere.sting 

 becau.se the pla.stids are definitely oriented with respect to the division 

 figures and becau>se they are distributed so that each pollen cell receives 

 approximately one-fourth of them. The cells are large, and both 

 pla.stids and chromosomes can be observed in living cells. The 12 

 pairs of chromosomes are nicely separated at late prophase, and one 

 of them is twice as large as the others. This point was previou.sly noted 

 by Cardiff (1906) and Ishikawa (1910). 



Smears stained in aceto-carmine were used for most of this study, 

 but smears were also fixed in Flemming's weak and chrom-acetic-urea 

 and stained in iron-haematoxylin, Flemming's triple, and safranin and 

 light green. The plastids are ea.sily observed in aceto-carmine since 

 the large starch grains resist the carmine, remaining a transparent 

 green while the rest of the cytopla.sm stains pink, and the chromosomes 

 bright red. The starch grains stain a deep blue in iodine, but show no 

 color in Flemming 's triple or haematoxylin. With the former a layer 

 of gentian, with the latter a layer of bluish-black cytoplasm, surrounds 

 each .starch grain. Unless one had examined the pollen mother cells 

 before fixation, he might easily interpret the plastid-bearing area in 

 fixed material as an unusually coarse cytoplasmic mesh. This is 

 probably the reason why the phenomena de.scribed below have not been 

 previously ob.served. 



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