l""n!^, Marcifal'To.] Microscopic StructuTe of Plants. 1 61 



of the Asclepiadaceae and Apocynaceae still more closely resemble 

 bast-j&bres, having the same thickened and striated walls. They 

 are sometimes found in the place of the true bast-fibres, and are 

 often united in a bundle along with the bast-fibres in the Phloem. 

 Other modifications are to be found in Arum, Acer, Oleander, &c. 



Peculiar laticiferous tubes have been described by Hanstein as 

 occurring in the onion. They contain a milky juice, and are long 

 wide cells with cribriform walls. They exist in the bulbs and stems 

 of several species of Allium, and are found to occur more freely in 

 the bulb. Similar structures containing a fluid that is not milky 

 occur in Narcissus, Leucojum, Galanthus, &c., the cells containing 

 numerous Eaphides. Other structures resembling laticiferous vessels 

 are to be found in Scilla, Ornithogalum, &c., and tubes containing 

 enormous Eaphides are to be met with in plants belonging to the 

 Order Commelynaceae. Bounded cavities containing elongated cells 

 filled with a milky juice have been described by Hildebrand as 

 occurring in the leaves of Psoralia hirta. 



Glands consist sometimes of single cells, at other times of groups 

 of cells, and are generally easily distinguished from the cells in their 

 immediate vicinity by their contents, such as oil, resin, colouring 

 matters, &c. Many hairs are to be considered as glands, secreting 

 pecuhar matters, as stinging hairs. The epidermal cells may also 

 secrete, as in the case of Lychnis viscaria, and the sweet materials 

 secreted by many petals. Single glandular cells are to be met 

 with in the prunitive tissue of the leaf of the Camphor plant, while 

 in many other plants groups of these cells are to be found. The 

 formation of the material contained in these glandular cells seems 

 to be a destructive process, the protoplasm disappeaiing and the 

 cell-wall becoming variously modified. This is to be seen in the 

 glandular hairs of Cannabis, Humulus, and Dictamnus. 



Eesin canals are to be met with in all the different tissues — 

 Limitary, Primitive, or Fibro-vascular bundles. They are inter- 

 cellular spaces, filled with peculiar oily or resinous materials. In 

 general they follow the course of the fibro-vascular bundles, and do 

 not anastomose. They are to be met with in Conifers, Cycadaceae, 

 Terebinthaceae, Umbelliferse, Araliaceae, and Compositae. The canals 

 of the Coniferae and Ivy seem to be the best known. 



VOL. III. M 



