36t> NATURAL SCIENCE. December, 1896. 



the nuclei contracts towards the centre, forming there a spherical mass. 

 This central mass then becomes differentiated into an external very 

 dense layer (periplasm) and a central vacuolate mass (gonoplasm). 

 The nuclei at the same time undergo division, and their number 

 becomes doubled ; the division is the typical indirect division of higher 

 plants. They then become almost completely restricted to the 

 periplasm, and there appears in the central part of the gonoplasm a 

 deeply staining granular mass, in which one of the nuclei becomes 

 embedded. This proves to be the nucleus that fuses with the one 

 brought by the fertihzing tube. 



In the antheridium also the nuclei divide, and one of the daughter 

 nuclei passes with a small quantity of protoplasm into the fertilizing 

 tube, which is protruded from the antheridium. This tubes bores its 

 way into the oogonium and through the periplasm and gonoplasm, 

 till it comes in contact with the central mass of dense protoplasm. 

 The antheridial nucleus is then expelled and is found in close contact 

 with the nucleus of the oosphere. At this stage a delicate membrane 

 becomes visible round the oosphere, and the two nuclei shortly fuse 

 together and fertilisation is complete. 



The cell-wall of the oospore is formed from the mass of the 

 periplasm, and the nuclei, which were embedded in it, degenerate. 

 Thus, of the numerous nuclei present in the oogonium and antheri- 

 dium, only one from each organ takes an active part in fertilisation. 



Botanical Crumbs. 



At a recent meeting of the Manchester Philosophical Society a 

 paper by the late Mr. Thomas Hick was read, in which the affinities 

 of Rachiopteris, a fossil plant of doubtful position, are discussed. The 

 name was given by Williamson to some plant remains from the lower 

 Coal Measures of Halifax, which he thought might be true ferns. 

 From an examination of the anatomy of this fossil, which has a 

 dichotomously branching stele, Mr. Hick concludes that Rachiopteris 

 cannot possibly be a root, but is probably a stem or leaf-structure of a 

 plant having more affinity with ferns than with lycopods. 



At the same meeting Mr. J. H. Ashworth. described the structure 

 and contents of the tubers of an hepatic, Anthoceros tuberosus, from the 

 banks of the Swan River, West Australia. These tubers, which are 

 attached to the lower surface of the thallus by a stalk, are well protected 

 b}' three or four layers of corky cells on the outside, while the interior is 

 filled with closely packed cells containing granules and oil-drops. 

 The granules give all the reactions for proteids, and seem to be 

 aleurone grains comparable to those forming the proteid reserve 

 material of seeds. Similar tubers were also found enclosed within the 

 substance of the thallus. Such well-protected resting organs, or 

 gemmae, are eminently adapted to preserve the existence of a 

 species in such a climate as that of West Australia, where periods of 

 severe drought have to be provided against. 



