440 THE MICROSCOPE. 



genie vessel the connecting branches are given off beneath each other, 

 so that the dots, which are rounded, are arranged in longitudinal rows j 

 but inthe acrogenic, or scalariforra, in which the vessels are generally an- 

 gular, and present distinct facets, the branches come off in the same 

 line, corresponding generally to the angles of the vessel ; the spaces left 

 between are linear instead of round. 



Mr. E. Quekett affirms, in opposition to the views entertained by 

 Mirbel, Kichard, and Bischoff, " that the dots left in these several vessels 

 are not holes, neither do they consist of broken-up fibre, but are the 

 membranous tubes, unsupported by internal deposit ; and on account of 

 the extreme tenuity of the tissue, and the minute space between the 

 fibres, the light in its transmission becomes decomposed, and appears of 

 a greenish-red hue. The structure of the dot is best seen by examining 

 the broken edge of any such vessels, when it will be found that the 

 fracture has been caused by the vessel giving way from one dot to another, 

 so that the torn edge of the membrane can be observed in each dot." 



PREPARATION OF VEGETABLE TISSUES. 



The proper mode of preparing and preserving vegetable tissues is a 

 matter of some importance to the microscopist ; we therefore propose 

 to add a few general directions for the student's guidance. 



Vegetable tissues are best prepared for the microscope by making 

 thin sections, either by maceration, by tearing between the thumb and 

 the blade of a knife, or by dissection. 



The spiral and other vessels of plants require to be dissected out 

 under a simple magnify ing-glass. Take, for instance, a piece of aspa- 

 ragus, and separate with the needle-points the vessels, which require to 

 be finished under a magnifying-glass, in a single drop of distilled water. 

 When properly done, keep in spirits of wine and water until mounted. 



Vascular tissue requires both maceration and dissection to its sepa- 

 ration. The cuticle or external covering of plants assumes various at- 

 tractive forms, best seen in the pelargonium, oleander, &c. j it may be 

 mounted either dry, or in Canada balsam. 



Cellular tissue is best seen in fine sections from the pith of elder, pulp 

 of peach, pear, &c. The petals of flowers are mostly composed of cellular 

 tissue, and their brilliant colours arise from the fluid contained within 

 the cells. In the petal of the anagallis, or scarlet chickweed, the 

 spiral vessels diverging from the base, and the singular cellules which 

 fringe the edge, are very interesting. The petal of the geranium, is one 

 of the most beautiful objects for microscopic examination. The usual 



