74 MICROSCOPIC FUNGI. 



chapter we have passed rapidly tlirougli four genera 

 of parasitic fungi so nearly allied_, that one is almost 

 led to doubt the validity of the generic distinctions. 

 These may be presented briefly thus : — 



Spores two-celled PucciNiA. 



„ tliree-celled Triphragmium. 



„ four to seven-celled Aregma. 



„ many-celled Xenodochus. 



It has been seen that the habit^ mode of growth^ 

 germination_, and structure^ except in the number 

 of cells^ scarcely difier ; but it is not om* province 

 here to enter upon the discussion of such a subject. 

 The association of one- celled^ orange-coloured 

 spores with the brown two or more celled spores- 

 passed in review is another feature worthy of 

 a passing notice^ and which opens a field for dis- 

 cussion. It is generally admitted that these two^ 

 forms are the production of the self-same mycelium 

 or vegetative system,, but it is not so .generally- 

 admitted that they are but two forms or phases 

 of the fruit of the same plant. It is not at all 

 uncommon in the history of mycology to find two 

 forms which were for a long time considered to be 

 distinct plants producing different forms of fruit, 

 and which bore different names, and were located 

 in different genera, at length proved to be only the 

 self-same plant in diff'erent conditions, and ending 

 in one name being expunged from the list. Such 

 a fate probably awaits, at no distant date, the orange 

 spores which precede or accompany the species in 



