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V. On the Mode of Development of the Pollinium in Asclepias Cornuti, Decaisne. By 
Tuomas Н. Corry, M.A., F.L.S., M.R.I.A., Shuttleworth and Foundation Scholar, 
Gonville and Caius College, and Assistant Curator of the University Herbarium, 
Cambridge. 
(Plate XVI.) 
Read December 21st, 1882. 
So far as I have been able to ascertain, no observer has fully investigated, іп an 
adequate manner, the whole mode of formation of the pollen-mass, or pollinium, in this 
genus and in the natural order to which it belongs. 
Hofmeister* and Schacht } alone have thrown some light upon its history in the early 
stages, with, however, somewhat contradictory results, while Schleiden's $ account of it is 
incorrect in several respects and very fragmentary. Francis Bauer, Ehrenberg $, Robert 
Brown |, Adolphe Вгопопіат є, and the younger Reichenbach **, have all recorded 
details more or less exact concerning its structure, but principally in some of the later 
stages, when the flower is becoming rapidly mature. 
In the very young anther, which has the form of a very slightly flattened spatula 
with a strongly convex dorsal surface, I was able to trace in transverse section that a 
single cell of the hypodermal row lying laterally but towards the internal side of each 
lobe of the anther, and containing granular protoplasm and a prominent nucleus, had 
undergone longitudinal division parallel to the long axis of the anther. This hypo- 
dermal cell in which division occurs constitutes the archesporium of Goebel тт. The 
archesporium so divided consists, therefore, of an inner and an outer segment. The 
inner segment in each lobe is in reality the primary mother cell of the pollen (Pl. ХУТ. 
figs. 1% 2, ртс). Each of the primary mother cells, as seen in transverse section, will 
be found, when viewed longitudinally, to correspond to a single longitudinal row of some- 
what cubical cells, rather higher, however, than they are broad or long. Since only a 
single row of primary mother cells is formed in each lobe, the anther is bilocular from 
the beginning, and never at any period quadrilocular. Тһе outer or more superficial 
segment of the primitive archesporial cell then becomes successively divided longi- 
tudinally in a tangential plane, in such a manner that in transverse section three layers 
Of cells are now apparent. In these latter, radial, horizontal, and further tangential 
* « Zur Entwickelungsgeschichte der Zostera,” Bot. Zeit, viec No. 7. pp. 121-131, plate iii. 
T Das Mikroskop, 2. Aufl. p. 166 et seq. 
i Grundzüge der wissenschaftlichen Botanik, dept 1850. 
§ Linnea, iv. p. 94; also Trans. Roy. Acad, of Sciences, Berlin, Nov. 1831. 
|| Linn. Trans. vol. xvi. p. 717 et seg, 1833. 
€ Ann. des Sci. Nat. Ser. i. vol. xxiv. pp. 263-279, pls. 13-14 В. 
** De Pollinis Orehidearum Genesi ac Structura: Leipsie, 1852. 
tt * Beitrüge zur vergleichenden Entwickelungsgeschichte der Sporangien," Bot. Zeit. 1881. 
SECOND SERIES.— BOTANY, VOL. II. N 
