1885.] NEW-YORK MICROSCOPICAL SOCIETY. 9 



after the first faint appearance of the nucleus, I have not yet 

 been able to determine." 



[Brown believed that the tubes proceeding from the pollen, 

 which he calls mucous cords, do not themselves enter the ovules, 

 but that they generate other tubes, the immediate agents of im- 

 pregnation ; and he states that the latter are " remarkably and 

 irregularly flexuose, apparently from the numerous obstacles 

 they have to overcome after leaving the cords and beginning to 

 mix with the ovula."] 



In a still later paper, " Supplementary Observations," London, 

 1833,'' he describes his further examination of Asclepias purpu- 

 rascens. " On the 12th of the present month (July) I succeeded 

 in tracing the pollen-tubes in that species not only over the 

 whole ovuliferous surface of the placenta, but also going off to 

 the ovula, to a definite point of each of which a single tube was 

 found in many cases attached." 



In 1835 Corda published his " Beitrage zur Lehre von der Be- 

 fruchtungder Pflanze."^" He was probably the first to announce 

 the observation of the entrance of pollen-tubes into the micro- 

 pyles of ovules in the Gymnosperm^, and he followed them to 

 the embryo-sac in the Coniferse. He says (I quote from Dr. 

 Gray's translation), "By a careful examination of the cavity of 

 the ovule in the fruit of Pinus with a lens, or even by a close in- 

 spection with the unassisted eye, grains of pollen may be seen re- 

 posing in its orifice. If we lay open the cavity in the scale by 

 taking off the covering, removing at the same time the primine 

 of the ovule which is originally adherent to the scale, we observe 

 the pollen-tubes, which have reached from the pollen to the en- 

 dostome of the secundine." 



About the year 1837, Schleiden advanced the theory that the 

 embryo is formed in the ovule at the time of impregnation by the 

 contents of the extremity of the pollen-tube, and does not exist 

 before the introduction of the tube. He says,^^ " At the flowering 

 period, the pollen falls upon the stigma, and then commences 

 the development of the reproductive cells. Each grain extends 

 itself into a long filament, * * * * ^^d in this form 



9Loc. cit., pp. 549, 550. 

 1 oActa Acad. Leopold Carol. Nat. Cur., Vol. XVII.; translated, and prefaced by re- 

 marks on the history of the subject, by Dr. Asa Gray, in Am. Journ. Sci., Vol. XXXI. 

 (1st Series), p.308. 



11" Die Ptlanze " ; translated by Arthur Henf rey, under the title, " The Plant ; u 

 Biography," London, 1848, p. 71, PI. III. flgs. 6-9. 



