CHAPTER II. PLANT TISSUES. 169 



Recapitulation of Tissues. 



1. — Parenchymatous Series. 



1. Parenchyma, or soft tissue. 



2. Collenchyma, or thick-angled tissue. 



3. Sclerotic parenchyma, or stony tissue. 



4. Epidermal, or boundary tissue. 



5. Endodermal Tissue. 



6. Suberous, or corky tissue. 

 II. — Prosenchymatous Series. 



7. Wood, or libriform tissue, also called woody fiber. 



8. Tracheids, or vasiform cells. 



9. Ducts, or vascular tissue, including : 



a. Dotted ducts. d. Annular ducts. 



b. Scalariform ducts. e. Recticulate ducts. 



c. Spiral ducts. /. Trabecular ducts. 



10. Hard bast tissue, or liber fiber. 

 III. — Sieve Series, including only 



11. Sieve, or cribriform tissue. 

 IV. — Laticiferous Series, including 



12. Laticiferous, or milk tissue, of which there are two 

 varieties : (a) Simple. (£) Complex. 



Intercellular Spaces. These are cavities, sometimes 

 minute and sometimes of considerable size, found chiefly in 

 mature tissues. Their contents are various ; sometimes they 

 contain only air ; at other times, water, crystals, milky or resinous 

 secretions, etc. 



They are formed in different ways ; sometimes by the splitting 

 of the common cell-wall which separates adjacent cells, a mode 

 of formation described by the term schizogenous, and sometimes 

 by the rupture and destruction of certain cells, a process 

 described by the term lysigenous. Examples of the former are 

 the small triangular intercellular spaces in the pith of the Elder 

 and in parenchyma tissues generally, and the large, and com- 

 paratively regular air-spaces in the stems of the Water-plantains, 

 Arums and Water-lilies ; of the latter, the hollows in the stems of 

 Equisetums, Grasses, Umbelliferae, Composite, Labiatae, etc. 



