STRASBURGER : FERTILISATION OF PHANEROGAMS. 1 59 



again, Strasburger finds reason to dissent from the current doctrine, 

 and interprets the two cells differently, looking upon the small cell as 

 the generative, and the large one as the vegetative cell. The partition 

 between the two cells is sooner or later dissolved, and if this does not 

 occur prior to the formation of the pollen-tube, the generative cell 

 travels bodily into the tube, having previously separated itself from 

 the wall of the grain. Even in the ripe pollen-grain, Strasburger is 

 able, by the aid of staining fluids, sections, &c., to demonstrate the 

 presence of nuclei, and can even distinguish between the nuclei of 

 vegetative and generative cells. The nucleus of the larger cell, how- 

 ever, often assumes special forms at the time of maturity, and may be 

 much reduced, though our author knows of no instance in which it 

 becomes totally disorganised while within the grain. The nuclei of 

 the generative and vegetative cells enter the pollen-tube, but not in 

 an absolutely fixed order. In the majority of plants the vegetative 

 nucleus goes first, but there are numerous exceptions. The nucleus 

 of the generative cell always doubles itself at least, either in the pollen- 

 grain or the tube, and, as already stated, the generative cell sometimes 

 enters the tube as a whole. The two generative cell-nuclei formed 

 in this way are not dissolved, but rather enter with the pollen-tube 

 into the interior of the ovule, as does also the vegetative cell-nucleus 

 in Monocotyledons. In the Orchidese, for example, it is easy to 

 demonstrate the vegetative and the two generative cell-nuclei within 

 the tip of the pollen-tube as it enters the micropyle of the ovule, the 

 vegetative being a little in advance of the generative. In Dicotyledons 

 it is otherwise. Here the vegetative cell-nucleus disappears earlier or 

 later in the pollen-tube, and only the two generative cell-nuclei enter 

 the ovule. These facts Strasburger considers as evidence in favour 

 of his interpretation of the nature of the two cells whence these nuclei 

 are derived, as well as of his view that the vegetative cell-complex is 

 not to be regarded as a rudimentary prothallium. 



Having thus summarised the results of his investigations on the 

 pollen-grains of Angiosperms, Strasburger concludes this section with 

 a brief account of the plants he has employed, arranged in systematic 

 order under their natural families. From this it is evident that the 

 conclusions arrived at are based upon an extensive series of observa- 

 tions on plants belonging to numerous natural orders, and are there- 

 fore entitled to respect and confidence. The details given of the 

 mode of treatment adopted in each case, and the results obtained, are, 

 however, the most valuable feature of this summary of the plants 

 dealt with, as they will enable all who desire to do so, to test the 

 truthfulness of the author's statements. 

 [To be continued^ 



Feb. 1885. 



