VESSELS. 



13 



find the two fragments united to each other by filaments, similar 

 to spider's web, which are, in fact, the unrolled tracheae. 

 Sometimes, instead of being formed of a single spiral thread, 

 these vessels are composed of two or three parallel threads rolled 

 together. Their length is, in general, very considerable, and it 

 seems that they terminate in a point at each extremity ; they do 

 not branch or ramify like blood-vessels in animals, and ordinarily 

 they are united in bundles. 



16. The false trachea, which are also called annular, or 

 radiated vessels, are unramified lubes, marked by transverse 

 parallel rays (fig- 6, e). When the rays are very close toge- 

 ther, these vessels resemble tracheae very much, but they are 

 not elastic and cannot be unrolled. 



17. The punctuated or dotted vessels (fig. 5) are cylindrical 

 tubes like the preceding, but their parietes are dotted with 

 small opaque points arranged in parallel or oblique series. 

 They were formerly called porous vessels, because it was be- 

 lieved that these dots were holes, but we are now assured that 

 they are not pores. 



18. The reticular vessels are cylindrical tubes, the surface of 

 which being covered by oblong transverse spots, gives them the 

 appearance of a net. 



19. The mixed vessels are tubes which at different points in 

 their length seem to possess alternately the characters of the three 

 kinds of vessels we have just mentioned. 



20. The moni'liform, or bead-like vessels, are 



punctuated tubes 

 which ramify, and 

 are contracted or 

 strangulated at dif- 

 ferent points (fig- 7). 

 Many botanists sup- 

 pose they consist of 

 series of cells at- 

 tached to each other, 

 end to end. 

 Fig. 8. VESSELS. 21. The proper vessels (fig. 8, 



Explanation of Fig. 7. Moni'liform (bead-like) vessels, magnified. 



Explanation of Fig: 8. Vertical section of a stem, showing cellular 

 tissue with elongated cells (a) ; and the reservoirs of the peculiar or proper 

 juices (J>, 6). 



16. What are false tra'cheae ? 



17. What are punctuated or dotted vessels ? 



18. What are reticular vessels ? (Reticular ; from the Latin, rete, a net.) 



19. What are mixed vessels ? 



20. What is meant by moniliform vessels ? (Moni'liform, from the 

 Latin, monile, a necklace, a string of beads, and forma, form.) 



21. What arfe proper vessels? 



m 





.-.a 



