INTRODtrCTION TO CRYPTOGAMIC BOTAKY. 249 



walls vary much in thickness, masses are formed, of such ex- 

 treme delicacy as hardly to outlive a slight rush of wind ; or 

 so hard as to endure the waste of the exposure of years to the 

 elements. The tips of the threads, again, often anastomose, 

 so as to form a close cellular tissue, in which the passage from 

 dissepimental walls and threads is almost imperceptible, as in 

 many Alg^. In some instances, as in the edible genus 

 Cyttaria, the walls of the component cells in certain parts are 

 so thick and gelatinous as to admit of comparison with the 

 thick coated cells of the foliaceous Algae, In some instances 

 the gelatinous element, as in the Myxogastri, is so predomi- 

 nant and in such a state of fluidity as to baffle research. The 

 younger state of most of these bodies is at present almost 

 unknown, and all that has yet been made out of their mor- 

 phosis, is derived from inspection of specimens, in which the 

 gelatinous condition was in the act of transition to the fila- 

 mentous and furfuraceous. 



243. In the milky Agarics, and in some closely allied 

 Russulce, Corda has detected a system of cells, which may be 

 considered identical with the vessels of the latex in Ph^no- 

 nogams. These cells, however, in point of structure, do not 

 seem to differ from others, though they are ramified. They 

 appear to be free from dissepiments and distinguished only 

 by their form and by the peculiar substance which they 

 contain. 



244. Fungi differ no less in size than in texture ; some are 

 amongst the most minute productions of the vegetable world, 

 while others are a yard or more across ; in almost every case, 

 however, the reproductive bodies are minute, though varying 

 from the twenty-thousandth to the two-hundred-and-fiftieth 

 of an iQch in diameter. 



245. The localities they affect are as various as their forms. 

 Wherever there is moisture combined with a proper degree of 

 temperature, together with organic matter. Fungi are capable 

 of existence. The spores of the Penicillium,, which infested 

 the bread some years ago in Paris to such an alarming extent, 

 were capable of sustaining a heat equal to that of boiling 

 water without losing their power of germination, and it is cer- 



