326 Scientific Proceedings, Royal Dublin Society. 



Summary. 



1. The first section of the paper deals with some points in the anatomy 

 of the microstrobilus of Larix leptokpis, but especially with certain pecu- 

 liarities in pollen grain development. 



2. There are very definite sacs in the microsporophyll apex, especially in 

 the bud. From a comparison of similar structures, as well as vegetative 

 buds in other genera, it is claimed that the evidence is in favour of the paired 

 cavities in that apex being homologous with the paired canals of the vege- 

 tative leaf and not with abortive sporangia. 



3. The normal grain, shed with stalk and generative nucleus already 

 formed, is wingless, large, with two very marked cellulose walls bounding 

 the prothallial cells, and the vestiges of a cellulose wall surrounding the 

 generative nucleus. 



4. In development, the first division may be very large— one-third or 

 even one-half of the original cell — due to the obliquity of the first division 

 spindle even through a right angle. In the latter case, very complete double 

 grains are formed ; in the former, the resultant divisions are also followed. 

 The whole is very similar to the irregular pollen-grain development in Picea 

 canadensis. 



5. The capacity for division of prothallial cells is thus not confined to the 

 Araucarians and the Podocarps. 



6. In wingless pollen, and in the possession of marked apical cavities in 

 the microsporophyll, especially in the bud, Larix and Pseudotsuga agree, in 

 marked contrast to the other Abietinean genera. 



7. The paper deals with some points in the anatomy of the female 

 strobilus and gametophyte of Larix leptolepis. 



8. There is a gradual transition from basal vegetative leaves to cone 

 bracts, as in Pseudotsuga. 



9. The ovule has a micropylar pollen-receiving device similar to 

 Pseudotsuga. 



10. The female gametophyte develops as in other Abietineae ; but the 

 megaspore membrane, very thick below, fades over the top ; the archegonia 

 are long and five in number : the neck cells are in one or two layers of four 

 to eight cells ; the archegonia may touch so that individual jacket layers 

 may coalesce or fade. It is strikingly similar to the female gametophyte of 

 Pseiidotsuga. 



11. In contradistinction to this genus, only those pollen grains which 

 reach the nucellus develop pollen tubes, and none such were seen till June 

 had well begun. 



