314 Scientific Proceedings, Royal Dublin Society. 



little distorted by plasmolysis. It is without wings — a well-known fact 

 which merits repetition, as even in the revised edition of Coulter and 

 Chamberlain's text-book (3), the impression is given that Pseudotsuga is 

 remarkable as the wingless Abietinean. That it does share this characteristic 

 with Pseudotsuga is of interest. Usually, though by no means always, it is 

 shed with the stalk and body-cell already cut off, as in Pseudolarix, Picea, and 

 Abies. The nuclei at this stage are always extremely compact and deeply 

 staining. On the whole it is a large grain, and when its definite prothallial 

 cells and variations are later on demonstrated, it should help finally to 

 disprove the hypothesis that in the Cupressineae, Taxineae, and Taxodineae 

 the lack of prothallial cells is to be regarded as an adaptive reduction of 

 weight in the absence of any aids to flight (Eobertson (20)). 



The two prothallial cells are comparatively large, and are most clearly 

 bound by regular cellulose walls. The wall of the second prothallial cell 

 joins that of the first, and the wall of the latter is in a very definite continuity 

 with that of the intine. But the unusual appearance is presented of two 

 horn-like growths running out from the innermost wall and fading away in 

 the cytoplasm. In some grains the appearance is so definite as to be re- 

 markable. One such is PI. XVII, fig. 6. Here the prothallial walls are 

 massive, the second prothallial cell being so large that its nucleus has gone 

 back to the typical resting stage before degenerating. The generative nucleus 

 has not divided in this grain, and the horns give one the impression of a 

 degenerated wall which normally should bound the generative cell. 

 PI. XVII, fig. 7, is a photomicrograph of the grain to show that the drawing 

 is in no way exaggerated. PI. XVII, fig. 8, also justifies this interpretation. 

 In this grain, too, the generative nucleus has not divided, while only the 

 cytoplasm of the tube-cell appears, although its nucleus was visible in the 

 next section on the slide. Here, owing to plasmolysis, the continuation of 

 the horns can be clearly seen swinging round the generative cell. Only one 

 such cell was found, and unfortunately the encircling wall was not quite 

 continuous on the left. On the right another thin membrane loses itself in 

 the cytoplasm. Whether the surrounding wall was a cellulose wall or only a 

 plasmic layer was not determined, as it was only found, of course, when the 

 slide was fully stained and finished. Fortunately, owing to plasmolysis, it 

 was free from the cytoplasm on both sides ; and, though thin, it was quite 

 distinct, and stained definitely blue with iron alum haemotoxylin, just as the 

 normal intine, prothallial walls and horns always do. 



It is worthy to note, in passing, that this grain may explain an earlier 

 and peculiar account of the pollen grain of Larix europea. Tschistiakoff (28) 

 describes its development in these words (p. 100): — "Drei aufeinander 



