CRYPTOGAMIA FUNGI. 109 



analogous, in some respects, to the tumours and ulcerations of 

 the animal system ; and we may, perhaps, form some idea of the 

 manner in which they may originate, by studying the various 

 galls and excrescences produced in plants by insects. We ob- 

 serve that the irritation caused by the deposition and evolution 

 of the egg Avill produce growths of the most curious kind ; and 

 differences in the irritation too slight to be traced, will occasion 

 very remarkable differences in the appearance of the growths. 

 Thus in the oak-leaf one insect irritation produces a globular 

 smooth ball ; another a depressed circular tumour, covered with 

 a hairy scarlet coat. The first is seated in the substance of the 

 leaf, and cannot be removed without destroying the texture of 

 the part ; the other seems almost placed on the leaf, and can be 

 detached with facility. Examples equally remarkable will occur 

 to every one who has paid any attention to this curious subject; 

 and the growths appear to be not less uniform and not less orga- 

 nized than many parasitical fungi. To suppose, therefore, that 

 the latter may be the result of irritations and obstructions in the 

 cellular parenchyma or in the circulating juices, seems not unrea- 

 sonable, although the sources of the obstruction or irritation may 

 be undiscoverable. 



* Fungi of a hard or corky texture. With a few exceptions, they are 

 very small, sessile, mostly of a black colour, never white : they grow 

 on wood and leaves generally when in a state of decay : tJieir seeds 

 are internal, immersed in a soft or pulpy parenchyma. 



-}- Seeds contained in slender crystalline tubes. 



66. SPH^RIA. Fungi globular or flask-shaped horny capsules, 

 naked or immersed in a corky or chared base, each open- 

 ing by a pore in the summit. 



G7. DOT HIDE A. Fungi wart or tubercle-like spots semi-im- 

 mersed in leaves, cellular within; cells excavated in the 

 mass, and without pores. 



68. FHASCIDIUM. Fungi solid roundish tubercles, opening with 

 a torn stellated orifice ; parasitical on leaves. 



