230 



THE MICROSCOPE. 



a small circular or oval spot, fig. 156: the latter may 

 occur singly, or be crossed by another at right angles, 



Fig. 134. 



1, Vertical section of root of Alder, with outer wall. 2, A vertical section of a 

 leaf of the India-rubber tree, exhibiting a central gland. 



which gives the appearance of a cross, as in fig. 161, Nos. 3, 

 4, a vertical section of fossil wood, remarkable for having 

 three or four rows of woody tissue occupied by large pores 

 without central markings." 



Plants are likewise furnished with lactiferous ducts or 



tissue, the proper vessels 

 of the old writers. These 

 ducts convey a peculiar 

 fluid, called latex, usually 

 turbid, and coloured red, 

 white, or yellow ; often, 

 however, colourless. It is 

 supposed they carry latex 

 to all the newly-formed 

 organs, which are nourished 

 by it. The fluid becomes 

 darker after being mounted for specimens to be viewed 

 under the microscope. This tissue is remarkable from its 

 resemblance to the earliest aggregation of cells, the yeast- 

 plant, and therefore has some claim to being considered 

 the stage of development preceding that of the reticu- 



Fig. 135. Lactiferous tissue. 



