29.] 



CHAPTER II. THE TISSUES. 



141 



These cells are frequently arranged in longitudinal rows : for 

 instance, the tannin-sacs of the Hop ; the sacs containing raphides 

 and mucilage in Tradescantia and many other Monocotyledons ; 

 the gum-resin sacs (" vesicular vessels ") of the bulb-scales of the 

 Onion; the sacs containing crystals of calcium oxalate in the 

 cortex of many woody 

 Dicotyledons ; the sacs 

 containing milky juice 

 or latex (commonly 

 gum-resin) in the Syca- 

 more, the Convolvu- 

 laceae, and the Sapo- 

 tacea3 (especially in 

 Isonandra Gutta, the 

 latex of which consti- 

 tutes gutta-percha). 



d. Laticiferous vessels. 

 These structures re- 

 semble the sacs con- 

 taining milky juice 

 (latex) in the nature 

 of their contents, and 

 differ from them struc- 

 turally only in that the 

 walls between adjacent 

 cells have become ab- 

 sorbed, thus forming 

 syncytes (p. 91). 



In the simplest case, 

 the laticiferous vessel 

 merely consists of a 

 longitudinal row of 

 cells whose transverse 

 septa have become ab- 

 sorbed, thus forming a 

 syncyte of the nature 

 of a vessel. When two 

 such vessels are in con- 

 tact laterally, the cell-walls are absorbed at the point of junction, 

 and in this way a continuous system of laticiferous vessels is 

 formed. This occurs in the greater Celandine (Chelidonium 



FIG. 105. Laticiferous vessels from the cortex of 

 the root of Scorzouera Uispanica, tangential section. A 

 Slightly magnified ; B a small portion highly magni- 

 fied. (After Sachs.) 



