THE PALM-STEM. 25 



perceived most clearly when a longitudinal section passes 

 through the adjacent walls of two scalariform ducts, in 

 which case we recognise distinctly that the slits are actual 

 excavations in the walls of the vessels, and not elevations, 

 as stated by Bernhardi (Ueber Pflanzengefasse, p. 35), 

 Treviranus (Beitrage, p. 22), and Meyen (Phytotomie, 

 p. 253), but that the interspaces between the slits form 

 elevations which project into the vessel. It may likewise 

 readily be perceived that a membrane is stretched between 

 the fibres, separating the fibres of the two vessels under 

 the from of a simple, dark line. The development of 

 these vessels shows that this membrane forms a tube 

 inclosing the fibres. The pores and slits equally exhibit 

 an evident rim, which does not depend, as Mirbel assumes, 

 on the presence of a projecting border, but is, on the con- 

 trary, caused by the borders of the slit being truncated 

 by an oblique surface. 



In many cases, as in Calamus for example, the place 

 where two vascular tubes are connected is conspicuous, 

 from each tube ending in a broad ring ; the two adjacent 

 rings form a band surrounding the vessel, as Moldenhawer 

 has shown long since in other plants. When the tubes 

 meet by such a ring, they are freely open to each other. 

 In other cases, on the contrary, particularly in Desmoneus 

 mitis, Cocos nucifera, Mauritia vinifera, armata, Kunthia 

 montana, Astrocaryum gynacanthum, vulgar e y Coryplia fri- 

 gida, such rings are seen at the points of connexion of the 

 tubes, and in these are found septa. The existence of 

 such septa is indeed denied utterly by all phytotomists ; 

 but having observed them hundreds of times, not only in 

 the Palms, but in many other Monocotyledons, and even 

 in many cases in the porous vessels of Dicotyledons, I do 

 not hesitate to assert their existence in the most positive 

 manner. The direction of these septa is usually such 

 that we obtain a front view of them in a longitudinal 

 section made in the direction of the radius of the stem. 

 They differ completely from all other membranes of plants, 

 in being formed of a reticulation of thick fibres, with 

 large openings between them. In the stems of Palms 



