Winton — Anatomy of the Fruit of Cocos nucifera. 273 



Cambiform cells occur singly, in rows and in groups among 

 the sieve tubes and also at the edges of the phloem. Those 

 among the sieve tubes are for the most part small (about '003 mm 

 in diameter), prismatic and with abundant protoplasmic con- 

 tents (fig. 6, c 1 ). They correspond to the " geleitzellen " of 

 Wilhelm, Tschirch* and other authors except that the walls 

 adjoining the sieve tubes, so far as the writer has observed, are 

 not pitted. 



At the edges of the phloem, particularly adjoining the 

 xylem, the cambiform cells are larger (often -01 mm in diameter) 

 and are often empty. The differences between these forms 

 are, however, so slight and perplexing that the writer, follow- 

 ing the example of De Bary and Strassburger, prefers to 

 group them all under the head of Cambiform cells. 



(e) Intercellular spaces, such as occur in the protoxylem of 

 many monocotyledinous plants, are seldom, if ever, seen in coir 

 libers, but oftentimes, although less commonly than in the hard 

 shell, the phloem and part of the xylem are destroyed during 

 growth, leaving a channel in the bundle. 



3. Endocarp. 

 This coat, known commonly as the shell (tig. 8, end), is a 

 dense aggregation of stone cells, among which run longitudi- 

 nally partially destroyed bundles. 



(a) The stone cells with their thick, deep yellow walls, 

 branching pores, and dark brown contents, present a striking 

 and characteristic appearance. They are either isodiametric or 

 strongly elongated, the latter (often 0'2 mm long) being usually 

 spindle or wedge-shaped, although hammer-shaped, hooked and 

 various other curious forms abound. 



A study of sections shows that the elongated cells are 

 arranged in groups, commonly with the longer diameters in 

 tangential-transverse directions and are best seen in cross sec- 

 tions of the shell (fig. 8, qst), but in some groups, particularly 

 those adjoining the bundles, they pass longitudinally about the 

 shell (tig. 9, 1st). It is evident from fig. 8 that more than half 

 of all the stone cells are tangentially-transversely elongated. 

 Those which appear isodiametric (1st) are partly cells which 

 are isodiametric in three dimensions and partly longitudinally 

 elongated cells in section. 



Groups of thinner-walled cells with dark brown contents are 

 occasionally met with. 



The brown contents of all the endocarp cells react the same 

 as the brown impregnating material of the mesocarp. 



(b) Vascular bundles are studied with difficulty in the 

 mature shell. By the rupture of the phloem and part of the 



*See Tschirsch, Angewandte Pflanzenanatomie. Wien, 1889, p. 349. 



