CELLULAR TISSUE. 



419 



secretions are furnished with glands, a circumstance which has led to 

 the division of woody tissue into simple and glandular. A large cen- 

 tral gland is seen in a section of a leaf from the Ficus elastica, India- 

 rubber-tree, No. 5, fig. 199. Professor Quekett says, "The nature of 

 the pores, or disks, in conifers, has long been a subject for controversy ; 

 it is now certain that the bordered pores are not peculiar to one 

 fibre, but are formed between two contiguous to each other, and 

 always exist in greatest numbers on those sides of the woody fibres 

 parallel to the medullary rays. They are hollow ; their shape bicon- 

 vex, Nos. 3, 4 ; and in their centre is a small circular or oval spot, 

 No. 6, fig. 199, and Nos. 1 and 5, fig. 198: the latter may occur 

 singly, or be crossed by another at right angles, which gives the ap- 

 pearance of a cross. No. 2, fig. 19 9-, is a vertical section of fossil 

 wood, remarkable for having three or four rows of woody tissue occu- 

 pied by large pores without central markings." 



At No. 7, fig. 199, we have represented fragments of Durham coal, 

 composed almost entirely of woody cells, in which are two flattened 

 spiral bands interlacing each other at regular distances, and having 

 small central spaces between them.* 



Plants are likewise furnished with lactiferous ducts or tissue, the 

 proper vessels- of the old writers. These ducts convey a peculiar fluid, 



WIKB 



Lactiferous ti$s^te. 



fig. 200. 



Reticulated ducts. 



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 aggre- 

 gation of cells, the yeast-plard > and therefore has some claim to being 

 considered the stage of development preceding that of the reticulated 



* In the January number, 1854, of the Microscopical Journal will be found a most 

 interesting account of the microscopical characters of coal, by Professor Quekett. 



