In forest trees, these unisexual flowers are usually borne on separate individuals of the same species, or the flowers on one tree are wholly staminate, and those on the other altogether pistillate. It must be obvious that such plants are still more unfavorably situated for fertilization. The great abundance of pollen produced compensates for the unfavorable situation of the flowers. The wind drives it far and near, and the air becomes sometimes so charged with it that rain, in falling, brings it down to the ground in considerable quantities, producing the so called sulphur showers of which we read in history. There is no doubt, also, that the bee and other insects in search of honey convey the pollen from the stamens to the pistils in unisexual plants. CELESTIAL PHENOMENA.--MARCH. BY D. W. BELISLE. ARGO NAVIS.--This beautiful constellation occupies a large space in the southern hemisphere, though few of its stars are seen in our latitude. It is situated south-east of Canis Major, and may be known by three stars forming a small triangle in the prow and deck of the ship. Sixteen degrees south of this triangle is a very brilliant star in the row-lock, called Naos. This star is the south-east corner of the Egyptian X, and comes to the meridian on the 3d of March, when, for a few hours only, it is visible in our latitude. It is then eight degrees above the horizon. Seven degrees south of Naos, on the 7th of March, may be seen Gamma, a brilliant star which, for a few moments, skims the horizon, and then disappears. It is never in our latitude more than one degree above the horizon, and is rarely visible. Thirty-six degrees south of Sirius is Canopus, a star of great brilliancy and beauty. It is of the first magnitude; but, having a south declination of fifty-three degrees, it cannot be seen in the United States. Twenty-five degrees east of Canopus is Miaplacidus, a star of the first magnitude in the oars of the ship. This is also invisible to us. This constellation contains sixty-four stars, which, seen from the southern hemisphere, are of singular beauty and brilliancy. "There they stand, Shining in order, like a living hymn Written in light." According to Greek mythology, the ship was placed in the heavens to perpetuate the expedition of Jason into Colchis to recover the Golden Fleece. Hebrew mythology also claims the origin of it, and with them it perpetuates Noah's Ark, in which a remnant of every living thing was saved during the deluge. There is good foundation for the supposition that the Argonautic expedition is founded on certain Egyptian traditions relating to Noah's Ark, and that the Greeks located them within their territory, and claimed them as a triumph of Neptune, the god of the sea. * * * * *