54 Linnean Society. [Feb. 4, 



slender tubes, furnished on the sides parallel to the medullary rays 

 with one or more rows of circular or angular dots ; but in Cycadee 

 no such uniformity is observable, their tissue, as in other phsenoga- 

 mous plants, consisting of two kinds of vessels, namely of slender 

 transparent tubes, without dots or markings, and of dotted, reticulated 

 and spiral vessels, which are capable of being unrolled. The former are 

 identical with the fibrous or woody tissue, whilst the latter, which form 

 a part of each bundle, can only be compared to the strictly vascular 

 tissue of other plants. These dotted vessels in Cycadece bear a con- 

 siderable resemblance to the vessels of Coniferce, and especially to 

 those of Dammara and Araucaria, from the dots being disposed in 

 rows, and confined to the two vertical sides of the vessel only, and 

 they are moreover alternate, as in the two genera just mentioned. 

 In Cycadeee, however, the dots present much less regularity in 

 number and size than in Coniferce, not only in different vessels of the 

 same bundle, but in different parts of the same vessel, forming one, 

 two, three, four, and five rows ; and they are not always confined 

 to the vertical sides, but appear in some cases to follow the entire 

 circle of the vessel. Their form is oblong, or elliptical, in Cycas re- 

 voluta, circinalis, glauca, and speciosa, Zamia furfur acea and puniila, 

 as well as in Encephalartos horridus and spiralis ; but they are 

 sometimes longer, narrower and nearly linear, giving the vessel 

 the appearance of being marked with transverse stripes. The 

 vessels in all present so much similarity, that no generic distinction 

 can be drawn from them. The dots are always arranged dia- 

 gonally. The dotted vessels of Zamia furfuracea and pumila 

 were observed to unroll spirally in the form of a band, pre- 

 senting a striking resemblance to those of Ferns. The band was 

 found to vary in breadth in different vessels, and was furnished 

 with transverse rows, composed of two, three, or more dots. The 

 coils followed the direction of the dots, and the unrolling was from 

 right to left. In Cycas revoluta dotted vessels frequently occur with 

 a single row of dots; but, from the circumstance of the dots on both 

 sides being in view at the same time, they are liable to be mistaken 

 as having a double row on each side. Besides the dotted vessels, 

 there occurs throughout Cycadeee another variety, differing but 

 little from the ordinary spiral vessel, except in the tendency of the 

 coils to unite. In some vessels the colls are free, and the fibre ex- 

 hibits frequently, at intervals, bifurcations or narrow loops ; in others 

 the coils unite at one or both sides, in which case the vessel presents 

 a series either of rings or bars ; the fibre then is with difficulty ua- 



