CLASSIFICATION OF VEGETABLE PREPAEATIONS. 403 



stems of plants ; in some transparent leaves they may be seen 

 in situ, or may be accidentally separated with the cuticle. 

 Very good examples will be found in the following plants : — 



Amadou, Canna bicolor, Lycopodium, 

 Asparagus, Hyacinth, Nepenthes, 

 Cactus opuntia, Lily, Mexican, Palm, 

 speciosa. Long leek, Rhubarb. 



Ducts of various kinds. — These, like spiral vessels, may be 

 dissected out of soft stems or roots after maceration, or may 

 be examined by vertical and horizontal sections of more dense 

 Structures ; the following plants wiU exhibit some of the most 

 interesting specimens : — 



Dahlia,. Opuntia vulgaris, Pteris aquilina, 



Elaterium, Phoenix dactylifera, Rhubarb. 



Woody Fibre. — This, although strictly cellular, is much more 

 firm and elastic than the usual forms of that tissue ; the walls 

 of the cells are for the most part structureless, whilst others 

 are covered with minute markings, or with glands, as, for 

 example, those of the coniferous tribe. The cells of woody 

 fibre maiy be examined in vertical and horizontal sections ; and 

 after long maceration, or by a process termed hackling, as in 

 the case of flax and hemp, may be separated from other 

 investing tissues. In the latter plants it may be seen in 

 its most simple condition, whilst, in sections, aU its peculiar 

 modifications can be examined ; the subjoined list will afford 

 some of the most characteristic examples : — 



China-grass, Sections of Date-palm, 



Flax, Drimys Winteri, 



Flax, New Zealand, Ephedra, 



Hemp, Nepaul wood. 



Sections of Araucaria, Pine, 



Cedar, Yew. 



Mr. Darker has long been known to microscopists for his 

 skill in making sections of wood. From the time the 

 achromatic microscope was first employed, he mounted sets of 

 sections made in three different directions, between glasses, 

 in the dry way, described in page 317. These served to 

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