84 



BOTANY. 



gives rise to a complex branching and anastomosing of the 

 spirals (Fig. 73, v'""). 



(3.) Scalariform vessels. These are prismatic vessels whose 

 walls are thickened in such a way as to form transverse 

 ridges, as described in paragraph 32, page 38. They are wide 

 in transverse diameter and their extremities are fusiform or 

 tiTincate (Fig. 73). 



(3.) Pitted Vessels. The walls of 

 these vessels are thickened in such a 

 way as to give rise to pits and dots, 

 as described in paragraph 31, page 

 26. The vessels are usually of wide 

 diameter ; in some forms they are 

 crossed at frequent intervals by per- 



FiQ. 74. 



Fis. 75. 



Fig. 74.— Pitted vessels of ArUtoloehia sip'o, from a lotgitudinal section of the 

 stem ; the vessel on ihe rigiit is seen in section, that on the left from without ; a.a, 

 rings, which are remnanta of the original transverse partitions ; 6, 6, sections of the 

 walls ; between the vesr^els are parenchyma-ceils, highly magnified. — After Duchartre. 



Fig. 75 — Tracheldes of Cytuus labvmum, from a longitndinnl targential section 

 of the htem ; m,m, a cross-section of a medullary ray ; in ilirceof the cells the pitted 

 partitions are seen ; the medulhiry ray is snrrourded by tracheldes, which are spi- 

 rally marked and sparingly pitted ; at ^, tvpo trachetdes have fused by the breaking 

 of the wall ; s, *, slightly modified cambium-cells. X 375. — After De Bary. 



74); 



m 



other 



forated horizontal or inclined septa (Fig. 

 forms they have fusiform extremities. 



(4.) Tracheides. These consist for the most part of single 

 closed cells, or of elements which closely resemble cells; 



