of Lathraa Squamaria, ^c. 407 



neath. One had a dark group of them under the fibre, but in- 

 stead of a regular set of tortuous vessels through its centre, it 

 had well-defined but mostly detached globules interspersed, 

 and indications of a tap striking downwards into the alburnum. 

 Several others had a tap in different stages of development, 

 sometimes irregular and ill-defined. In some, the globules 

 (which were filled with fluid) seemed to have formed fissures 

 or cavities in the alburnum, similar to those in Tab, XXIII. 

 Fig. 1. & 2 ; while many of the tubers were without either tap, 

 beaded vessels, or the transparent globules, and consisted only 

 of the delicate cellular substance already described. 



I think it probable that all these, including the section 

 Fig. 4, were tubers in the early stages of their action on the 

 parent root ; and that the globules interspersed in them and in 

 the bark and alburnum underneath, with a central tendency, 

 were preparing the way for the yet undeveloped inferior ap- 

 pendage or funnel. It is diflScult to conceive how so delicate 

 and succulent a substance can penetrate the comparatively hard 

 bark and alburnum of the root, but by means of some chemical 

 change, or corrosion effected by the union of their respective 

 juices. The irregular fissures or cavities in the alburnum ex- 

 hibited in Tab. XXIII. Fig. 1. 2. & 5, are generally present 

 under those tubers which have pierced it with their funnels. The 

 septa and parts immediately in contact are frequently brown and 

 discoloured, indicating disease from being drained of their sap. 

 They are always surrounded by a light-coloured border, as in 

 the figures, probably a new layer of liber formed by the reno- 

 vating power of Nature to check the progress of the morbid 

 action. Beyond this border, the surrounding parts are con- 

 stantly sound and healthy, the injured portion seldom extend- 

 ing wider than the space covered by the tuber. 



I am inclined to think that the tubers are renewed annually, 

 VOL. XVI. 3 G like 



