184 . MR. T. Н. CORRY ON ASCLEPIAS CORNUTI. 
It was conjectured by Count W. Е. Gleichen *, even so far back as the year 1779» 
although his description of the floral mechanism by which it takes place is in most 
points far from accurate, and he himself never observed the actual modus operandi. 
Notwithstanding the fact that he observed the pollinia attached to the lower ends of the 
lateral angles of the style-table, 7. e. in the place where Brown afterwards found them, 
and producing each a cord of pollen-tubes which passed from thence to the apices of the 
styles, he does not seem ever to have known exactly the precise value of his own obser- 
vations; for he considered that if the plants are ever fertilized by the agency of insects 
(though in what way he does not state, and the extraction of the pollinia by them was 
quite unknown to him), it is the exception rather than the rule. 
Christian Konrad Sprengel, in his classic work * Das entdeckte Geheimniss der Natur 
im Bau und in der Befruchtung der Blumen,’ published in 1793 t, was the first to 
observe the method by which the pollinia are extracted by insects in Gomphocarpus 
fruticosus, В. Br. (Asclepias fruticosa, L.). These visit the flowers for the sake of the 
nectar secreted by the corona. His account of this preliminary step in the process of 
pollination is in many respects admirable. But though Sprengel observed with accuracy, 
it happened, unfortunately for science, that a false and erroneous hypothesis lay at the 
basis of nearly all his work, since he imagined that self-fertilization and not cross fertili- 
zation was the rule; and it was on this aecount that he failed to realize the full value 
and use of the marvellously adapted mechanism which exists in these flowers. He 
believed that the pollinia, when withdrawn through this agency, were applied by the 
insect creeping over the flower to the upper slightly concave surface of the great style- 
table of that same flower from which they had been taken, the insect being intoxicated 
by the nectar in order to endow it with an extraordinary amount of activity, which he 
regarded as necessary, or at least advantageous, to the act of pollination. Of the real 
manner in which fecundation is accomplished, and of the proper stigmatic surface, he 
was entirely ignorant, and, moreover, he had also erroneous ideas as to the mode of 
action and structure of the corpusculum ; for, following Kólreuter, he imagined that it 
behaved after the fashion of a trap. But though such was Sprengel's view of the matter 
in regard to Asclepias and other plants in general, he seems to have had glimpses occa- 
sionally of the true state of matters; for on p. 43 of his work just quoted the following 
very remarkable and pregnant statement occurs :—** Since a large number of flowers are 
diclinous, and probably at least as many hermaphrodite flowers are dichogamous, Nature 
appears to have designed that no flower shall be fertilized by its own pollen." 
In 1831 Robert Brown | added several of the most important links to the chain of our 
* * Auserlesene mikroskopische Entdeckungen bei den Pflanzen, Blumen, und Blüten, Insekten und andern Merk- 
würdigkeiten,' Nürnberg, 1777-1781, pp. 73 et seq.; also translation into French by J. Е. Isenflamm, Nürnberg, 1790. 
+ Рр. 189-146, plate ix., figs. 4, 5, 10, 11, 38-41. 
$ ‘Observations on the Organs and Mode of Fecundation in Orchidew and Asclepiadew,’ printed for private distri- 
bution, Oct. 1831; Trans. Linn. Soc. vol. xvi. pp. 685-745, 1833, plates 34-36; and Misc. Bot. Works, vol. i. 
pp. 487-536, plates 30, 31, 32. Abstract of last, Philos. Mag. and Annals of Philosophy, Dee. 1831 ; also Edinburgh 
Jour. of Sci. vol. vi. pp. 174-183, 1832; also Flora, xv. pp. 353-366, 378-382, 673-676. ‘ Additional Observations 
on Ње Mode of Fecundation in Orchidew’ read June 1832, printed with the last in Trans. Linn. Soc. vol. xvi. and 
Mise. Bot. Works, vol. i. pp. 537-543. ‘Supplementary Observations on the Fecundation of Orchides and Ascle- 
piadew,’ printed privately, London, 1833; and Misc. Bot. Works, vol. i. pp. 545-551; also (in French) Guillemin's 
Archiv. Bot. vol. ii. pp. 324-329, 1833; and (in German) Flora, vol. xvii. pp. 17-24 (1834). 
