236 PROGRESS OF MICROSCOPICAL SCIENCE. 



which I am unable to determine the nature. These raphides are 

 minute, with feeble optical qualities, and their prismatic constituent 

 crystals not clearly discernible as is usual in this class of crystalline 

 cell contents. Their great number is the first thing one notices in 

 examining the section, and further study shows that the inner layers 

 of cells contain by far the greater number of them, very few cells in 

 this position being without one. The more external cells contain 

 fewer, the outermost cells none. The starch granules are very minute 

 and most numerous in the middle layers. Their polariscope reactions 

 are obscure. The ligneous cells are distributed in twos and threes, are 

 large, porous, much thickened, and the successive layers of thickening 

 deposits very evident without the aid of reagents. In conclusion it 

 may be remarked that the only difficulties in the examination of this 

 bark arise from the minuteness of the cells, and their being filled with 

 various matters that are difficult to remove without altering the general 

 structure. Maceration in very dilute sulphuric acid for a few hours 

 appears to be most effectual in preparing sections for examination, so 

 far as a general view of the size and shape of the cells is concerned. 



Pollen of Petasites fragrans. — A writer to ' Science Gossip,' who 

 signs himself Q. F., says that though this is not a British plant, as it 

 was originally introduced to England from Italy in 1806, it is doubtful 

 whether any of our indigenous species abound so much and so early 

 in pollen as P. fragrans, or Sweet-scented Butterbur. It grows ram- 

 pant at Canterbury in deserted gardens, where this Butterbur has 

 been profusely in bloom from Christmas to January. And the pollen- 

 grains are so remarkably beautiful as to afford very delightful micro- 

 scopic objects even at this season. Each pollen-grain is oval, having 

 a length of r ^ ¥ of an inch, and a breadth of -^^ ; muricated on the 

 surface like those of so many other composite ; becoming globular 

 or sub-triangular, with three scars appearing for the passage of the 

 future pollen-tubes, when treated with diluted sulphuric acid. The 

 pollen-grains are so large that they may be very easily examined 

 under an object-glass of half an inch focus. 



The Septic Virus. — The French paper, ' Union Medicale,' for 

 January and February of this year, contains an interesting account 

 of the researches of Davaine and others on this subject. A brief 

 sketch of these researches has been sent by Dr. B. Sanderson to the 

 ' Medical Becord.' From this we learn that M. Davaine's research 

 is a continuation of his former one on the induction of septicaemia in 

 rabbits by inoculation. As it deals with the fundamental experiments 

 on which he founds his claim to have discovered a new virus, it may 

 be taken, not only as the most recent, but the most complete exposi- 

 tion of his present position in relation to the subject. M. Davaine 

 uses the rabbit as a test for the detection of the septic virus in 

 blood. He finds (as others have done before him) that that animal 

 is specially liable to be affected by the introduction under its skin 

 of blood which has undergone a certain degree of putrefactive 

 change ; and he has endeavoured to measure the virulence of such 

 blood by comparative experiments, in which the activity of the liquid 



