PHANEROGAM I A : FLOWERS. 409 



base of the flower a whole mass of confervoid web, which consists of 

 entangled pollen-tubes emitted in this manner. Nay, in the anthers of 

 theAristolochiac(B, which usually secrete some sweet juice, thepolJen not 

 unfrequently emits tubes, which then, as I believe to have seen, come by 

 chance over the border of the anther on to the stigma, and so descend 

 into the cavity of the germen without waiting for the insects which here 

 so abundantly assist. 



History and Criticism. 



In many plants the pollen- tubes are so striking, even by their 

 mass, that, although every possible opinion but the true one was 

 entertained as to the behaviour of the pollen to the stigma, they 

 could not have been wholly overlooked, if it had only happened 

 to the few microscopic observers of the eighteenth century to have 

 examined the localities in which they occur. Horkel (op. cit.) has 

 collected the earliest traces of observation of them : Amici* made 

 the discovery that a tube is emitted by the pollen-granule and penetrates 

 between the papilla of the stigma; and was also the first who traced 

 the pollen-tube from the stigma to the micropyle, probably in Yucca 

 gloriosa.\ In the interval between these observations, however, Brong- 

 niart J had made known his far more comprehensive researches, in which 

 he observed the pollen-tube everywhere on the stigma, and in many 

 plants as torn extremities hanging out from the micropyle. These two 

 torn ends were then united by Rob. Brown (1831, 1832, 1833) in 

 applying Amici's discovery, with his well-known profundity and accuracy, 

 to two of the most widely distinct families, the Asclepiadacece and Orchi- 

 dacecB, and in both he placed the growth of the pollen-tube into the seed - 

 bud beyond doubt. I myself have extended Rob. Brown's observations to 

 a great number of families, and these observations, confirmed by Horkel, 

 were made known by him in the Monthly Report of the Berlin Academy of 

 Sciences, in August 1836, and by me in Wiegmann's Archives for 1837 

 (vol. i. p. 312. et seq.). Horkel's paper appears to have remained wholly 

 unnoticed, and thence many may have thought that they might quietly 

 set aside my observations, to put their crude observations, or often mere 

 opinions, in their place. Nevertheless, I might leave mine to themselves 

 as incontestible, under the aegis of observers like Amici, Rob. Brown, 

 and Horkel. Finally, WydlerJ of Bern observed the descent of the 

 pollen-tube and its entry into the seed-bud iu. several species of Scro- 

 phularia ; and Meyen likewise confirmed the correctness of the existing 

 observations, without specially naming the plants in which he had com- 

 pletely traced the pollen-tube, but giving abundance of matter in the 

 shape of observation of the entry of undoubted pollen-tubes into the 

 micropyle. Thus the fact, that in all Phanerogamia the pollen-tubes 

 descend to the seed-bud was admitted as a law, till recently Hartig^f 

 appears to have intended to upset the whole matter. In the first place, it 

 cannot but awaken a prejudice against his book, that instead of relating 

 unbiassed and accurately-observed facts, he at once spins out a new so- 



* Mem. di See. Ital. v. xix. pp. 253 257. (1823). 

 f Ann ties Sc. Nat. v. xxi. p. 331. (1830). 



\ Mem. sur la Generation et le Developpement de 1'Embryon, &c. Paris, 1827. 

 Observations on the Organs and Mode of fecundation in Orcliideac and A sell? - 

 piadese. London, 1833. 



|| Btbliotbeque Univcrs. de Geneve, Oct. 1838. 



f Neue Theorie der Befruchtung der Pllanzen, &c. Brunswick, 1842. 



