CELLS— FIBRES— VESSELS. 



149 



368. Cell-Shapes are various ; each plant being always true to its 

 own types. In the Elder and Water Crowfoot (Pig. 215, A, D) 

 the cells are dodecahedral — 12-sided ; in the Beet 

 (B) they are hexagonal; in the Bean (0) they are 

 ramose (branching) and stellate (star -shaped). 

 The cotton of the Cotton -seed (Fig. 216), 



Fig. 216.— Cells: A, Elder pith {Sitmhaem nigra). B, young cells of Beet (.Bela 

 vulgaris) : n, n, n, nuclei. • C, Beau {t'haseulus vutgaris). D, Water Crowfoot {Kanun- 

 cuius aqiiatilis), 



which gives us the most important staple of commerce, consists of 

 long, tubular hairs, each hair a single cell, which becomes flattened 

 and twisted as it ripens, and thus adapted for spinning. 



364. Cell-sizes vary also. The usual size is ^^^ to jj^ of an inch 

 in diameter. The Elder cell is ^^^ of an inch ; that of the Cork 

 only yj'o^y of an inch. 



365. Cell-markings. — The young cell at first has a wall of even 

 thickness. As it grows, it deposits an inner layer, which, however, 

 is interrupted, leaving thin places, called dots; through these the 

 fluids pass from cell to cell; the dot in one cell being complementary 

 to the dot in the cell adjoining. Difiisrent deposits give different 



markings ; so that we have Dotted, or Punctate, 

 .^',^^_ cells in the Elder (Fig. 217, A) ; Rayed and Reticu- 



late cells in the Mistletoe (B) ; Annular cells in the 



^-^m^mm 



Fio. 216.— Apex of a 

 cotton-seed {Qossypium 

 herbaceum) ; X 30 di- 

 ameters ; showing one 

 long hair, the rest be- 

 ing removed. The fine 

 down as seen on the 

 seed in the cut is in- 

 visible to the naked 

 eye. 



A 



riG. 217.— Cells: A, 'E\iei pith {Sambuma nigra). 

 C, Mistletoe (Kiscum aZ&uin). J), Oreltia Slorio. 



same (C) ; Spiral cells in the Orchids (D). In 

 the Conifers (Fig. 218) the thin places are cir- 

 cular and surrounded by a double ring ; they are 

 called Pits ; and these are Pitted cells. 



366. Cellular Tissue forms the pith of 

 all young stems ; the green pulp of leaves ; 

 the flesh of fruits; the fibrils of roots; 

 the tender parts in all new growths. It is 

 here called Parenohyma (Gr. parencMo, I pour in beside), 



13* 



