266 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



more than a year after pollination and from a week to ten days before 

 fertilisation, about thirteen months elapsing between pollination and 

 fertilisation. The Pines studied were Pinus Strobus, P. austriaca, 

 P. rigida, P. resinosa, and P. montana var. uncinata, the above applying 

 to all these. The authoress remarks that nuclear phenomena are found 

 to vary so much, even within the limits of a given genus, that it no 

 longer seems safe to consider the details of development in a single plant 

 as typical of a large group of plants. No generalisations, therefore, are 

 made for the Abictincce. Conclusions could not even be drawn for the 

 genus Pinus without hesitation, for " there may still exist within the 

 genus individuals which are, in certain aspects of nuclear activity, a law 

 unto themselves." One of the most interesting statements made is that 

 nothing suggestive of spermatozoids can be found in Pinus. It is inter- 

 esting in recollection of the fact that spermatozoids have been declared 

 by Dr. Hirase for Ginkgo (Salisburia), and that they have been found in 

 Cycas and Zamia of the allied but more ancient natural order, the 

 Cycadacecs. They are so large in Zamia that, according to Webber, they 

 may be seen by the naked eye. — B. I. L. 



Pollen Cells. 



Pollinium and Sperm-cells in Asclepias Cornuti. Decaisne, 

 The Development Of the. By C. Stuart Gager, Cornell University. 

 (Ann. Bot. vol. xvi., No. 61, p. 123; March 1902).— The flower of 

 Asclepias, we read, has always been of interest to botanists. " In 1831 

 Brown, who separated the Asclepiadeae as a natural order of plants from 

 the Apocyneas of Jussieu, made the first serious study of the pollinia. 

 His first paper on this subject appeared in 1809, but he failed to observe 

 the grains of pollen, and thought that the pollinium consisted of one 

 individual cavity filled with minute granular matter mixed with an oily 

 fluid." The views of Link, Treviranus, and Ehrenberg are then quoted. 

 " In 1833, as a result of further researches on the Asclepiadecs, Brown 

 describes the pollen mass on several species of Asclepias, particularly in 

 A. phytolaccoides and A. Curassavica, the figures being drawn by Bauer. 

 He then without doubt considers the cells of the pollinium as true 

 pollen grains." The modern literature on the subject is completely 

 reviewed by the author, and he gives his own work on the archesporium, 

 the tapetum, the primary pollinium cells, and their first and second 

 divisions, the origin of the sperm cells, and the germination of the 

 pollinium cells, in full detail. It is interesting to note that " a rather 

 vigorous circulation of protoplasm was noticeable in freshly germinated 

 pollen-tubes." In the summary it is stated that " the individual cells of 

 the pollinium of A. Cornuti are true pollen grains which never become free. 

 . . . The outer membrane of each pollen grain is composed of the wall 

 of the mother-cell (which does not dissolve) plus the cross walls formed 

 by the two divisions of the mother cell. Each pollen grain possesses an 

 inner membrane, which it develops about itself. The generative cell 

 divides, before the formation of the pollen tube, into two sperm-cells, 

 each of which travels down the pollen tube, passing the vegetative 

 nucleus on the way." A paper by Corry and two others by Fry and by 



