318 Corda on the Impregnation of Plants. 



as to the deposition of an aura seminalis, (the contents of the pol- 

 len-tubes.) He, however, did not see the entrance of the pollen- 

 tubes into the micropyle of the ovules. I had already seen the 

 pollen-tubes penetrate quite into the cellular tissue of the placenta 

 in Hyacinthus, Himatoglossum and Orchis maculata ; but it ap- 

 peared to me impossible, in this instance, to follow them farther. 



In the winter of 1833-34, I frequently repeated these observa- 

 tions on the Hyacinth, and saw the penetration of the pollen-tubes 

 into the placenta, without touching, however, the micropyle of the 

 ovules. During my residence in Berlin, I had the honor of showing 

 to his Excellency Freihern von Humboldt, and to Professor Kunth, 

 this penetration of the pollen-tubes into the placenta. At the 

 same time I was zealously engaged in researches upon the Cycadeaa 

 and Coniferae ; and concluded about the time of their flowering to 

 continue my experiments on the fecundation of the latter family, 

 since it bears naked ovules, and we can every year obtain large 

 quantities of ripe seeds. I was convinced that the penetration of 

 the pollen-tubes through the micropyle must certainly take place 

 in this family, but was far from imagining that such an interesting 

 and important series of investigations would arise out of the subject. 



By a careful examination of the cavity of the ovule in the fruit of 

 a Pinus with a lens, or even by a close inspection with the unas- 

 sisted eye, grains of pollen may be perceived reposing in its orifice, 

 (Tab. 42, fig. 1, a.) In this manner the pollen-grains of Larix are 

 represented by Nees von Esenbeck in his Genera Plantarum, (Vid. 

 a. a. O. fig. 7.) If we lay open the cavity in the scale, by taking 

 off the covering, (Tab. 42, fig. 3, h) removing at the same time 

 the primine of the ovule which is originally adherent to the scale, 

 (Tab. 42, fig. 3, c) we observe the pollen-tubes, (a. a. O. a.) which 

 have reached from the pollen to the endostome (Tab. 42, fig. 3, e^) 

 of the secundine (fZ.) But often the grains of pollen fall through 

 the exostome, (Tab. 42, fig. 3, e') and rest upon the orifice of the 

 secundine, (Tab. 42, fig. 3 and 4, d) i. e. the endostome, (e^) or 

 they sometimes fall into the cavity of the secundine, as may be per- 

 ceived in fig. 4, of Tab. 42, in fig. 14, of Tab. 43, and in fig. 21, 

 aai of Tab. 44. 



So far my observations demonstrate that the pollen-tubes pene- 

 trate into the micropyle and the endostome ; but in explaining their 

 further course it becomes necessary to recur to my researches upon 

 the ovules of Coniferae. My observations differ by no means from 



