142 Gager . — The Development of the Pollinium and 
the division of the primitive mother-cells in three planes at 
right angles to each other. 
Corry also observed two nuclei in the pollen-grain, but 
considered the smaller one the vegetative nucleus, and the 
larger one the ‘ active ’ nucleus. No mitotic figures are given 
by him, and he does not trace in detail the steps in the 
development of the pollen. 
There have also appeared two other papers on Asclepias 
since my own paper was completed, one by Fry (1901) 1 , and 
the other by Strasburger (1901) 2 . 
Fry considers the archesporium as multicellular, and states 
that the primary sporogenous cells become spore-mother-cells 
without further division. All the spore-mother-cells of a 
sporangium divide into four, but the exact number of chromo- 
somes in any division was not determined. The generative 
and tube nuclei are figured, and the author considers that the 
generative nucleus moves to the wall of the pollen-grain before 
division, and is cut off by a cell-wall. The fact that this nucleus 
was formed at its lateral location as a result of the position 
assumed by the nucleus of the young microspore before division 
was not observed. Fry also mentions and figures the rod- 
shaped bodies in the pollen-grain that stain like chromatin, 
but tests with several reagents failed to reveal their nature. 
Prof. Strasburger’ s paper is especially interesting from the 
fact that in 1889 he stated that the pollen-mother-cells never 
divide. In the first part of the paper is briefly discussed the 
literature concerning the homology between the pollen-mother- 
cell and the embryo-sac mother-cell, and the author refers to 
the fact that a shortening of the ontogeny, similar to that 
which takes place in the development of the embryo-sac of 
some plants, has never been observed in the development 
of pollen. 
Strasburger then takes up the case of Asclepias and reviews 
1 Fry, T. C., Development of the Pollen in some Asclepiadaceae. Bot. Gaz., 
vol. xxxii, p. 325, 1901. 
Strasburger, E., Eine Bemerkung zu der Pollenbildung bei Asclepias. Ber. d. 
deut. bot. Gesell., vol. vii, p. 450, 1901, 
