48 HALF-AN-HOUR AT 



vertical fibres placed opposite the intercellular passages or the 

 meeting angles of contiguous cells or ducts^ leaving regular slit-like 

 spaces opposite the cavities of the adjacent cells. This form is 

 especially characteristic of the Ferns ; but it occurs also commonly 

 in the Dicotyledons in a less regular form, passing quite insensibly 

 into Pitted Ducts, as in the wood of Eryngiian maritimufn ; the 

 scalariform vessels of Ferns are often slightly unroUable." — (Micro. 

 Diet, 2nd ed., p. 640). 



Ducts very similar are found in the Wheat Root, in the stem 

 of Vegetable Marrow, and elsewhere; indeed, I have often been 

 struck with the close similarity in structure between the ducts of 

 some common plants and those generally considered peculiar to 

 ferns. 



Sections of Sugar-Cane (Plate IV., Figs, i and 2). — The 

 transverse section is more satisfactory than the longitudinal, which 

 would have been better if put in glycerine. The type of struc- 

 ture is very interesting, as connecting our ordinary fistulose 

 grasses with the compound structure met with in palms. There 

 are in the sugar-cane smaller ducts having a structure I have not 

 met with elsewhere — viz., distant annuli with the walls of the 

 vessels closely porose. These should be exhibited, as well as the 

 ectoderm, the structure of which is highly characteristic. Pieces 

 of sugar-cane in the fresh state are not unfrequently to be met 

 with. 



Periploca Graeca, tr. sec. (PI. V.). — The special feature of 

 interest consists in the dark masses of inspissated proper juice. 

 Lindley tells us that "the milk of Periploca Graca is very acrid, 

 and has been employed by Orientals as a wolf-poison " (Lindley's 

 " Vegetable Kingdom," p. 626). I do not know the plant, which 

 belongs to the Asclepiadacece. This order contains the beautiful 

 Hoya carnosa and the singular Stapelias, the odour of whose 

 flowers is so foetid that they are commonly known by the name of 

 " carrion-flowers." Longitudinal sections showing the laticiferous 

 vessels and the ducts are required to complete the information 

 partially afforded by this specimen. In sections of the stem of 

 white poppy, the dark inspissated juice (opium) may be seen, much 

 as in the present slide. 



Rhubarb, long, sec (Plate IV., Fig. 3), showing spiral vessels 

 and raphides /// situ as an opaque object, was shown a short time 

 ago, and excited much interest in those who had the pleasure of 

 seeing it. Wishing to know more about it, I have ascertained 

 that it was a piece of one of the dead, decaying leaf-stalks, which 

 at the date of writing were to be obtained in plenty where the 

 plant is cultivated. These are to be cut in short lengths, then 

 made into thin slices, and slightly pressed. A slide so prepared 

 should be in every cabinet. 



