vii.] THE BRACKEN FERN. 57 



The dark-brown dots are scattered irregularly, but the 

 major part of the dark-brown colour is gathered into two 

 narrow bands, which lie midway between the centre and 

 the circumference. Sometimes the ends of these bands are 

 united. Enclosed between these narrow, dark-brown bands 

 are, usually, two elongated, oval, yellowish-brown bands ; 

 and, outside them, lie a number of similarly coloured 

 patches, one of which is usually considerably longer than 

 the others. 



A longitudinal section shews that each of these patches 

 of colour answers to the transverse section of a band of 

 similar substance, which extends throughout the whole 

 length of the stem ; sometimes remaining distinct, some- 

 times giving off branches which run into adjacent bands, 

 and sometimes uniting altogether with them. 



At a short distance below the apex of the stem, however, 

 the colour of all the bands fades away, and they are 

 traceable into mere streaks, which finally disappear alto- 

 gether in the semi-transparent gelatinous substance which 

 forms the growing end of the stem. Submitted to micro- 

 scopic examination, the white ground-substance, or paren- 

 chyma, is seen to consist of large polygonal cells, containing 

 numerous starch granules ; and the circumferential zone 

 is formed of somewhat elongated cells, the thick walls of 

 which have acquired a dark-brown colour, and contain 

 little or no starch. The dark-brown bands, on the other 

 hand, consist of cells which are so much elongated as 

 almost to deserve the name of fibres and constitute what 

 is termed sderenchyma. Their walls are very thick, and of 

 a deep-brown colour; but the thickening has taken place 

 unequally, so as to leave short, obliquely directed, thin 

 places, which look like clefts. The yellow bands, lastly, 

 are vascular bundles. Each consists, externally, of thick- 



