456 
AMERICAN JOURNAL OF BOTANY 
[Vol. io. 
threads suggests nothing unusual, unless it be that some of the threads fold 
on themselves and some do not, as the examination of several cells has led 
me to suspect. 
The direct origin of the chromosomes in the homoeotypic division from 
the chromatin masses in the daughter nuclei and the subsequent behavior 
of these chromosomes in the formation of the granddaughter nuclei are 
strong evidences in support of the theory of the permanence of the individual 
chromosomes. 
Summary 
1. Chromatin masses corresponding in number to the chromosomes at 
the time of cell division are present in the various stages of the vegetative 
cells and of the reproductive cells in Acer platanoides. 
2. These chromatin masses may be followed through synapsis, in which 
stage they become closely paired and unite end to end. 
3. The chromatin threads are formed by a flowing out of the chromatin 
material from the chromatin masses. 
j* 4. The chromosomes do not lose their individuality in passing through 
the telophase stages to the resting stage of the nucleus. 
Allegheny College, 
Meadville, Pa. 
LITERATURE CITED 
Cardiff, I. D. A study of synapsis and reduction. Bull. Torrey Bot. Club 33: 271-306. 
1906. 
Darling, C. A. Sex in dioecious plants. Bull. Torrey Bot. Club 36: 177-199. 1909. 
Digby, L. On the archesporial and meiotic mitoses of Osmunda. Annals Bot. 33:135-172. 
1919. 
Mother, D. M. Mitosis in the pollen mother-cells of Acer negundo, L. and Staphylea 
trifolia, L. Annals Bot. 28: 115-134. 1914. 
Overton, J. B. Ueber Reduktionsteilung in den Pollenmutterzellen einiger Dikotylen. 
Histologische Beitrage zur Vererbungsfrage. Jahrb. Wiss. Bot. 42: 121-153. 1905. 
——. On the organization of the nuclei in the pollen mother-cells of certain plants, with 
especial reference to the permanence of the chromosomes. Annals Bot. 23: 19-61. 
1909. 
Rosenberg, O. Uber die Individuality der Chromosomen im Pflanzenreich. Flora 93: 
250-259. 1904. 
EXPLANATION OF PLATES 
All figures were made with the aid of a camera lucida with Spencer 1.5-mm. objective 
and 1 ox eyepiece. Drawings magnified about 2900 diameters. 
Plate XXXI 
Fig. 1. Resting nucleus of the pollen mother cell, showing chromatin bodies, net-like 
linin, and bud on nucleolus. 
Fig. 2. Early growth period of the pollen-mother-cell nucleus, with a bud freed from 
the nucleolus. 
Fig. 3. Early growth period of cell, showing conspicuous pairing of chromatin bodies. 
Fig. 4. Early stage in synapsis, the linin becoming drawn into a mass and the chro¬ 
matin bodies often joined together end to end in pairs. 
