ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 319 



any line of demarcation between the two, the tissues arc continuous and 

 pass insensibly from one to the other. These facts suggested that the 

 scale in the pine-cone is a backward extension of the chalazal tissue of 

 the ovules. The cones in the Cupressinefe and Taxodineae are normal, 

 i.e. the inegasporangia are borne by the bracts or carpels which later 

 become enlarged. In the Araucariese there is a slight backward ovular 

 growth, but the bract is still so large as to greatly overshadow it. In 

 the Abietinefe the ovules, which at first are secondary to the bracts, 

 soon make so great a backward (or chalazal) growth as to greatly over- 

 shadow the bracts. A decreased development of the bract is associated 

 with the enlargement of the ovular tissue, which has assumed more and 

 more the functions elsewhere discharged by the bract. On this view the 

 male and female cones are strictly homologous ; and in the latter the 

 sporophyll enlarges or remains small just as the chalazal development 

 of the megasporangium into a scale is more or less pronounced. 



Gametophytes and Embryo of Podocarpus.* — W. C. Coker obtains 

 the following results. The pollen-grain contains two prothallial cells, as 

 in the Abietete ; and in all essential points the pollen-grains are similar 

 in the two cases. The second prothallial nucleus persists, and is found 

 later in the tip of the pollen-tube ; a behaviour which is unknown in 

 other Conifers and for which a parallel must be sought in GingJco and the 

 Cycads. The pollen-tube reaches the prothallium before the arche- 

 gonium initials can be distinguished ; only two cases were found showing 

 the male cells, but these leave no doubt that there is only one functional 

 male cell formed as in Taxus. The macrospore arises deep in the nucellus, 

 and is not surrounded by " spongy " tissue such as is general in the 

 Coniferte, and has often been erroneously described as of sporogenous 

 character. The outer layer of the prothallium is composed of very small 

 regular epidermis-like cells with dense protoplasm, but almost free from 

 the starch-grains which are abundant in other parts. The author re- 

 gards these surface cells as specially modified for secretion; no such 

 definite layer seems to have been described for other gymnosperms. In 

 one case two prothallia were found in one ovule ; neither had formed 

 archegonia, although the seed had reached its full size. One of them 

 contained a few tracheids ; a fact recalling the formation of tracheids in 

 apogamous fern prothallia. 



The number of archegonia was from six to ten. The neck varies 

 greatly both in shape and the number of the cells ; in one case more 

 than twenty-five were counted, and sometimes there were only two. 

 The jacket cells are less dense than in many other conifers, and their 

 nuclei do not go to pieces when the archegonium is mature. The 

 position and behaviour of the ventral canal nucleus agrees closely with 

 that in Taxodium. It is not separated from the protoplasm of the egg 

 by a membrane ; it persists for some time after fertilisation and probably 

 assists in nourishing the embryo. The pollen-tube penetrates for some 

 distance into the archegonium and discharges its contents into the 



Fertilisation stages were not found, but the author thinks it probable 

 that the fusion-nucleus moves to the base of the archegonium before 



^O ' 



* Bot. Gaz., xsxiii. (1902) pp. 89-107 (3 pis.). 



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