328 BOTANICAL GAZETTE [October 



The writer has had the opportunity of examining large quantities 

 of coniferous material of all the sub tribes, since his own studies 

 have been particularly in this group. The Abietineae, Arau- 

 carineae, Podocarpineae, Taxineae, and Cupressineae in the broad 

 sense, have all been studied in most of their genera, and in the case 

 of the larger genera in a number of species. Perfection of pollen 

 development was found to be characteristic of the micro sporangia 

 of this important group. The only case of pollen abortion which 

 has come to light during the present investigation is that furnished 

 by one species of Abies, to be described later. Fig. 9 illustrates 

 the pollen conditions in Araucaria Cooki, cultivated in a green- 

 house. It will be seen that the grains are all perfect, the difference 

 of size being due to their greater or less inclusion in the plane of 

 section. The greenhouse conditions have obviously not affected 

 the morphological perfection of the pollen. Fig. 10 shows part of 

 the same section under a higher degree of magnification. The 

 numerous prothallial cells, w r hich are a feature of the organiza- 

 tion of the gametophyte produced in the pollen grains of the Arau- 

 carineae, can be seen. 



The Gnetales have been studied in all their three surviving 

 genera. Welwitschia has entirely perfect grains. The same state- 

 ment holds for the three or four species of Gnetum which I have 

 examined in this connection. Two species of Ephedra were ex- 

 amined, with the result that the pollen appeared to be without 

 tendency to abortion. It is perhaps of interest to record, in this 

 connection, that the pollen of Ephedra and Welwitschia are strik- 

 ingly alike externally, both being characterized by spiral striation 

 of the external coat of the oval grains. This feature was not found 

 in the case of Gnetum. It has not been thought necessary to intro- 

 duce an illustration of the microspores of the Gnetales, although 

 several were prepared for this purpose. 



The Monocotyledons may next be considered. Fig. n shows 

 the pollen conditions in a wild species, Iris versicolor. The pollen 

 is obviously perfect in development. Many hybrids of the vari- 

 ous species of Iris are grown in gardens, in fact most of the 

 more attractive cultivated irises are the result of hybridization. 

 Fig. 12 illustrates the pollen conditions in a hybrid improvement 



