FUNGI. 141 



number of parasites are epiphytes, where the vegetative 

 portion is developed on the surface of the epidermis, and 

 only specialized branches, called haustoria, penetrate the 

 tissues of the host. The genera Astcrina and Erysiphe are 

 examples of the latter class. 



The tissues of fungi, even when very dense and wood- 

 like in consistency, consist of elongated cells or hyphce. 

 These hyphte are either continuous or transversely septate, 

 when the hypha consists of a row of superposed cells. 

 Again the hyphae may be simple or variously-branched ; 

 in the latter case the branches from the same or distinct 

 hyphae not unfrequently coalesce at the points where they 

 come in contact, and by the absorption of the walls at the 

 point of contact, establish a communication between pre- 

 viously isolated portions of the mycelium. Not unfrequently, 

 in the case of germinating spores, the mycelium forms a 

 very complex and irregular network, brought about in the 

 manner described above. The coalescence does not only 

 take place where two branches of mycelium come in contact 

 in the ordinary course of growth, but it has been clearly 

 demonstrated that branches are drawn out of their original 

 course through an angle of nearly ninety degrees, to form 

 a union with another branch. The cause and object of this 

 anastomosing are equally obscure ; it has been suggested 

 that it possibly serves to nourish every part more equably, 

 or may effect the equal distribution of certain substances 

 that are produced locally. 



A modification of the above, known as clamp -connec- 

 tions, takes place as follows. In a transversely septate 

 hypha a branch originates laterally immediately below a 

 septum, grows outwards for a short distance, then bends 

 until its apex comes in contact with the hypha just above 



