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 Freibern 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 Cycadee 
and Conifere ; 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. Iwas 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, 6) 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 (d.) 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*) oF 
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, 
aa! 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 Conifere. My observations differ by no means 
