1886.] Himalayan Spruce-fir (Abies smithiana) . 5 



When mature, the needles are clothed densely with a homogeneous 

 orange-red layer of spores forming elevated beds. These masses of 

 spores break out first in isolated spots along the lateral grooves on the 

 upper surface of the needle. Having once broken through the epider- 

 mis, they extend in area with great rapidity and soon coalesce. Ulti- 

 mately, they form two longitudinal beds on the upper surface separated 

 by a narrow groove in the middle line. Laterally, they creep round and 

 involve the lower surface to some extent. After the spores have burst 

 through the upper surface and have made some progress towards coales- 

 cence, isolated crops appear in two more or less parallel lines on the 

 lower surface of the needle. These ultimately form oval beds which do 

 not tend to coalesce as on the upper surface. When quite young, this 

 uredinal form emits a disagreeable and offensive odour which is absent 

 from the secidial form. 



Microscopic Characters, (a) Normal Structure of Needle. — The normal 

 needle is flattened laterally, and a transverse section is broadly quadri- 

 lateral (fig. 21). The extreme length of such a section about the middle 

 of the needle is about 1-09 m.m. and the breadth 0-76 m.m. The two 

 sides forming the upper angle are shorter than the two lower sides, and 

 include a larger angle. On either side, near the surface and about mid- 

 way between the upper and lower angles, are two resin canals, and in the 

 centre is a vascular bundle measuring 0"236 m.m. in diameter. The 

 needle is covered externally by a layer of epidermis cells whose contin- 

 uity is interrupted only by the interposition of stomata. In each 

 transverse section, generally six stomata may be seen, two on each of the 

 shorter sides and one on each of the longer ones. Immediately under 

 the epidermis, there is a layer of thick- walled hypodermal cells. This 

 consists of a single row of cells, excepting at the lower angle, where 

 it is double. It is interrupted at the stomata and at the resin 

 canals. These canals are bounded by two layers of cells ; the external 

 larger and thicker- walled than the internal. The canals measure 

 about 0'076 m. m. in diameter. The centre of the needle is occu- 

 pied by the vascular bundle, which in transverse sections is seen to 

 be limited by a circle of oval cells forming an endodermic sheath. Be- 

 tween these sheath cells and the hypoderma, lie large thin- walled paren- 

 chyma cells (the mesophyll) with numerous large air spaces. These 

 parenchyma ceils, as seen in transverse section, resemble, to some extent, 

 the palisade cells of ordinary leaves and are arranged radially ; but this 

 general radial symmetry is interrupted by a secondary crescentic system 

 around each of the resin canals. In depth, these cells vary from two to 

 four cells. They are filled with chlorophyll corpuscles, starch grains, 

 and protein bodies, the relative amounts varying with the season and 



