52 BOTANY. 



stemg of our woody trees there is but very little of the fun- 

 damental system present, making up the very small pith and 

 the thin plates (medullary rays) running radially through 

 wood and hark. 



95. In its fullest development the fundamental system 

 may contain soft tissue (parenchyma) of various forms, 

 thick-angled tissue, stony tissue, fibrous tissue, and milk- 

 tissue. Their arrangement, within certain limits, presents 

 a considerable degree of similarity in nearly related groups 

 of plants, but this is by no means as marked as in the case 

 of the fibro-vascular system. 



96. (1) Soft tissue (parenchyma) is the most constant of 

 the fundamental tissues; it makes up the whole of the in- 

 terior plant-body in those plants where there has been no 

 differentiation into more than one tissue, and it is present 

 in varying amounts in all plants up to and including the 

 highest. 



97. (2) Thick-angled tissue (collenehyma) when present, 

 as it generally is in the stems and leaves of flowering 

 plants, is always either in contact with or near to the epi- 

 dermis. 



98. (3) Stony tissue (sclerenchyma) is common beneath 

 the epidermis of the stems and leaves of flowering plants and 

 ferns, and the stems of mosses. It sometimes appears to 

 replace thick-angled tissue. Some elongated forms of stony 

 tissue are scarcely to be distinguished from fibrous tissue. 



99. (4) Fibrous tissue occurs in some leaves and stems 

 near to the epidermis. In ferns it forms thick band-like 

 masses, giving strength to the stems. 



100. (5) Milk-tissue (laticiferous) may occur, apparently, 

 in any portion of the fundamental system of flowering 

 plants, 



