44 Mr. Griffin on an Improved Method of Preparing Oxygen Gas. 



Meyer maintains that the pollen tube becomes united to the embryo 

 sac, and that at the point of union a small protuberance originates, 

 which becomes the germinal vesicle ; this vesicle being formed of two 

 cohering membranes, viz., that of the end of the pollen tube, and that 

 of the apex of the embryo sac. The germ vesicle gradually expands 

 in length, and grows into the depth of the embryo sac, becoming a 

 cylindrical tube from the end of which a simple round cell separates, 

 constituting the young embryo. 



The opinions of Brongniart, Endlicher, linger, Gleichen, and Bern- 

 hardi were then noticed; and the curious experiments of the latter, 

 relative to the hemp plant were detailed, from which he was led to 

 conclude that perfect seeds could be produced without the influence of 

 the pollen. 



Dr. Balfour remarked, in conclusion, that ho was disposed to adopt 

 the opinion that the formation of the embryo sac and of the primary 

 utricle took place before the emission of the pollen ; that the primary 

 utricle was not the extremity of the pollen tube, nor a mere involution 

 of the embryo sac ; and that the act of impregnation consisted in the 

 fovilla being brought into contact with the embryo sac, and by a cer- 

 tain unknown influence determining the formation of the embryo-cell. 



XIII. — On an Improved Method of Preparing Oxygen Gas. 

 By John Joseph Griffin. 



Equal parts by weight of Chlorate of Potash and Black Oxide 

 of Copper, well dried and 

 finely pounded, are inti- 

 mately mingled. This mix- 

 ture is well adapted for the 

 extemporaneous preparation 

 of oxygen gas. When exposed 

 to a gentle heat, it becomes 

 red-hot, and disengages a 

 rapid current of pure oxygen 



gas. The best vessel to use for the experiment is a hard Ger- 

 man glass tube, about an inch wide, and six inches long, con- 

 nected by a long and sound cork with a gas-leading tube of 

 not less than half-an-inch bore : a smaller tube will not carry 

 off the gas with sufficient rapidity. 



The tube may be half filled with the mixture, and must be placed 

 nearly in a horizontal position, over a small spirit-lamp. The incan- 

 descence appears very soon after the flame is applied to the tube. It 

 rapidly extends through the whole mixture, and the operation is then 

 at once ended ; the discharge of gas ceases suddenly. What remains 

 in the tube is a dry coarse black powder, resembling gunpowder, which 

 does not adhere to the glass, but can be readily shaken out. It consists 



