698 MR JOHN M<^'LEAN THOMPSON ON 



have been traversed in Section V., which was taken immediately below the style; 

 and in fig. 33, which depicts a section, VI., passing through the style, nine 

 anthers are represented. The naked filament belongs to the right neighbour of 

 the anterior stamen. The naked filament was that of the stamen which was longest 

 at this stao-e. 



It will be remembered that, when the lateral zygomorphy had become distinctly 

 marked in all fiowers previously examined high on the raceme, the extreme right 

 stamen of the anterior group possessed the longest filament. It will, however, be 

 understood that at the early stage represented in the series of sections the lateral 

 zygomorphy had not yet dominated the antero-posterior zygomorphy. 



For the present it will suffice to note that in sections of the type figured no 

 differences of anther condition were observed. 



It was then evident that in the departure from staminal actinomorphy to lateral 

 zygomorphy the alterations which had been observed in the stamens were due 

 entirely to inequalities in the lengths of the filaments. 



An anatomical study of these was then made. 



It seemed, however, that the stamen-filaments should be studied developmentally 

 in a number of flowers which appeared to be perfectly actinomorphic, for it was 

 considered advisable to determine the conditions of the filaments in such forms in the 

 bud, and the developmental stages reached by them when the anther is completed and 

 when it is about to dehisce. 



The stamens of a number of flowers in which I failed to detect any departure from 

 the actinomorphic conditions were accordingly studied. The results of the anatomical 

 examination of one form — Staphylea j^'^nnata L. — will be given, before briefly 

 considering the filaments of Greyia Sutherlandii. 



At dehiscence the stamens of this plant slightly overtop the petals, and are about 

 ^ inch in length (fig. 14). It was impossible to cut perfectly radial sections which 

 would include the median longitudinal plane of the filament and a portion of the 

 anther in which a loculus was clearly shown. Sections were, then, cut in a plane 

 departing slightly from the radial plane, but including median longitudinal sections of 

 the filaments with a fair portion of a loculus. The accompanying figures were drawn 

 from these later sections. 



Figs. 26, 27, 34 represent stamens forty-eight times as large as they were at the 

 corresponding stages, while figs. 20, 35, 37 are twenty-four times as large as the actual 

 objects. 



Fig. 26 represents a very young stamen. The filament is short, and not more than 

 nine cells are found in each longitudinal row of ground-tissue. These minute cells are 

 of fairly uniform size, and no special conductive strand is observable. In the anther 

 the archesporium is difl'erentiating. 



In fig. 27 a much more advanced stage has been reached. The filament is about 

 eighteen cells in length, the box-shaped cells of the ground-tissue being counted. 



