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PART II. - VEGETABLE HISTOLOGY. 



cells, like those represented in Fig. 417, the end ones taper- 

 pointed, the middle ones blunt-ended, and together forming a 

 combination shaped like a wood cell. Such tissue is termed 

 wood parenchyma, and the name happily expresses its intermedi- 

 ate character. 



Fig. 418. 



Fig. 419. 



Fig. 420. 



Fig. 421. Fig. 422. 



Fig. 418. — A dotted or pitted duct from Milk-weed; magnified 200 diameters. 

 Fig. 419. — Part of a scalariform duct from a fern; magnified 150 diameters. 

 Fig. 420. — Spiral ducts: a, one with a single spiral band; /', one with a triple spiral — 

 magnified about 250 diameters. 



Fig. 421. — An annular duct from house Geranium; magnified about 300 diameters. 

 Fig. 422.— A reticulate duct from house Geranium; magnified about 300 diameters. 



(9) Ducts or Vascular Tissues. These, as we have seen, 

 differ from wood tracheids, mainly in being composed of two or 

 more cells which have become confluent end to end, forming 

 tubes of varying length. Their diameter is commonly large, 

 compared with that of the wood cells of the same plant, and 

 they are usually much longer. When mature, their walls are 



