224 A. Barclay — On a neio Species of TJredine [No. 2, 



tlie most injurious consequences to its welfare. The f angus is confined 

 entirely to the leaves, the mycelium never being found in the tissues of 

 the stems bearing affected needles. The mycelium is therefore not 

 perennial. Before entering upon a description of the structure of the 

 fungus and of its morphological relations to its host, it is necessary to 

 give an account of the normal structure of the needle. 



Normal Structure of Deodar Needle. — The transverse section of a 

 young normal needle is broadly quadrangular, one angle being superior, one 

 inferior, and two lateral ; the superior angle is truncated and grooved ; 

 as the needle gBOws older, however, the upper angle becomes gradually 

 flattened until at last the section of an old needle is more triano^ular 

 than quadrangular (fig. 8). On each of the four sides of the young 

 needle there are as a rule four longitudinal rows of stomata, and on 

 either side of the needle a resin canal, one of which is always larger than 

 the other, though both are of the same structure. The centre of the 

 needle is occupied by the wood bundle, the xylem being below and the 

 phloem above. 



Looking next to the more minute structure of the tissues of the 

 needle, it will be observed that the needle is clothed externally by a sin- 

 gle layer of epidermis cells. Under this is a layer of thick- walled hypo- 

 dermal cells, interrupted opposite the stomata, and double at the angles 

 and between the stomata, where there is only space for a single cell ; 

 this layer is double also at each side of the resin canals. These cells 

 are from three to four times as long as they are broad, and the epidermal 

 cells are about one-third the length of the hypodermal cells. The resin 

 canals are clothed internally by a layer of thin- walled epidermis cells 

 supported externally at about three places by a second layer of similar 

 cells : the whole is surrounded by a layer of sclerenchyma fibres, 

 except where the canal is bounded by the hypodermal cells. Below the 

 hypodermal layer follow large parenchymatous chlorophyll-containing 

 cells radially arranged. These cells internally abut against the cells of an 

 endodermal sheath surrounding the central vascular bundle, much in the 

 same way as that in which palisade cells of leaves generally abut against 

 the spongy tissue. This parenchymatous tissue is loose with numerous 

 large air-cavities. The cells of the endodermal sheath are closely conti- 

 guous laterally, and are densely filled with starch grains. They are 

 large cubical cells nearly twice as long as they are broad. The tissues 

 enclosed by this sheath are : — (a) in the centre the xylem and phloem 

 divided into two lateral divisions ; the xylem being below : (h) beyond 

 the phloem a group of much thickened sclerenchyma fibres : beyond 

 these again and between them and the endodermis, (c) a set of large 

 water- containing cells with numerous bordered pits. Laterally the place 



