LECT. IV.] THE ROOT. BUJUBS. 181 



the inner surface studded with opaque slightly 

 elevated glands, which produce correspondent 

 depressions on the outer surface of the next layer. 

 The other layers are fleshy and thick in proportion 

 as they approach the enclosed plantule, or centre ; 

 and, although the depressions of the glands be 

 visible on the exterior of each, yet, from the tur- 

 gidity of the cellular texture, neither these nor 

 the vessels are perceptible in them ; but by placing 

 the bulb in a coloured solution for twenty-four 

 hours, and then making a transverse section of it, 

 the latter are seen like coloured points arranged in 

 a regular series, and nearly equi-distant from the 

 enclosing epidermis of each layer*. By tearing 

 the layer longitudinally opposite to any of these 

 points, the vessels can be traced downwards 

 through the substance of the layer, and even into 

 the radical plate. 



In this bulb, the stem, which bears both the 

 foliage and the flower, rises from the centre of the 

 bulb ; but as soon as the new bulb, which is 

 formed close to its base, enlarges, the enclosing 

 laminae of the old one Jbegin to lose their suc- 

 culency and plumpness ; and this exhaustion con- 



* Plate 3. fig. 5. a transverse section of a Tulip bulb, du- 

 ring the flowering season, a. Section of the stem ; b. remains of 

 the exhausted layers of the old bulb ; c. the new bulb, which 

 should flower next season ; the dots in the layers showing the 

 positions of the longitudinal bundles of vessels. 



N3 



