428 ■ Scientific Proceedings, Royal Dublin Society. 



account of the protoplasm contracting but slightly, the space between 

 the mass of protoplasm and the wall appearing to be the wall itself. 

 In the terminal cell becoming vertically septate [A, indica), and the 

 resemblance to a bone {A. Napoleon III.), we trace the transition 

 to the most differentiated form, A. tenella, which is very distinct 

 in habit and flower from all the others, while in the strikingly 

 similar (to A. arvensis) Lysimachia nemoruni the stamens are 

 quite glabrous. The pollen in the five species just described is 

 somewhat triangular in outline. 



A. tenella. — Filament woolly, with pluricellular hairs, the 

 lower segments of which resemble dumb-bells, with knobs project- 

 ing from the ends at right angles to the long axis ; they might 

 also be likened to metacarpal bones, as before mentioned. Ter- 

 minal cells much smaller, rounded, arranged in a kind of ear- 

 like form, arising from repeated transverse and vertical septa ; 

 all with a delicate spiral striation (pi. xx., fig. 17). Diameter 

 •0007-"0012 (across knobbed portion). In the young bud we find 

 hairs in all stages, from the simple pluricellular form of A. jjhil- 

 lipsii to the fully developed form. Pollen small, smooth, oval. 



AcANTHACEJE. 



Hairs occur in many genera and species, and vary a good 

 deal, but are generally pluricellular, often presenting two or more 

 types on different parts of the same stamen [Acanthus, Tkimhergia). 

 In Acanthus the - hairs are very largely developed, the anther 

 having quite a brush-like appearance. 



Acanthus spinosus. — Hairs occur both on anther and at base of 

 filament. Those on the anther are of two forms — [a) short and stiff, 

 forming a dense brush on the ventral suture of the anther, with 

 the surface reticulated in a labyrinthiform manner; {b) on the 

 dorsal portion of the anther, longer, more flexuous, stronger walls, 

 and with only longitudinal striae. The position of these dorsal 

 hairs varies according to whether the anthers are those of the 

 interior or exterior pair of stamens, the anthers of the latter being 

 closely appressed to each other by their ventral sutures. The 

 basal hairs resemble those dorsally situate on the anther. Their 

 diameters are about the same, viz., '0010 in. (pi. xix., fig. 18). 

 Pollen oval, slightly papillate. 



