Paraphyses. 29 



CHAPTER X. 



PARAPHYSES AND THEIR FUNCTION. 



Paraphyses are variously shaped often hair-like, or capitate unicellular 

 bodies, sometimes accompanying the spores, and are just branches of the 

 hyphae not concerned in, but accessory to, reproduction. These sterile fila- 

 ments may occur in the spermogonia, where they assume the form of stiff 

 hairs projecting from the mouth, and possibly serve to retain the spermaitia 

 until they are carried away and distributed by insects. 



But it is in the uredo-layer that they are most commonly met with, and 

 there they are of various shapes. They are recorded in Australian species 

 of Puccinia, Phragmidium, Melampsora, and in Uromyces phyllodiorum, 

 and along with other characters may be useful in the discrimination of 

 species, as in Puccinia magnusiana, Koern., where they at once distinguish 

 it from the other species occurring on Phragmites communis. They usually 

 surround and arch over the spore-bed, and the apex is often swollen in a 

 globose or clavate manner. 



Their principal function is probably the same as that of the hairs, in 

 some grasses and other plants to protect the spores when exposed by the 

 rupture of the cuticle against excessive evaporation and consequent drying up 

 during ,the day, and to moderate the temperature in the cold nights. 



In the genus Melampsora and some species of Puccinia and Uredo, e.g., 

 the uredo of P. poartim, P. magnusiana, and U. spyridii growing on hosts in 

 damp situations or along rivers and in moist valleys, the paraphyses have 

 always swollen capitate heads, and their function is suggested by their 

 structure and position. The wall is much thickened, so as to leave a very 

 small cavity in the head, and in the stalk it may become so thick as 

 completely to obliterate the cavity and thus render it solid. The 

 thickened head has a great capacity for retaining moisture, and since they 

 are crowded together and over-lap the spores, they will prevent them from 

 getting soaked and at the same time protect them against excessive evapora- 

 tion, which would have a drying effect according to Dietel 9 . 



Their great function is as protective organs when the spores are exposed 

 by the rupture of the cuticle, and Plowright compares them with the 

 pseudoperidial cells of the aecidiospores. He has made observations on 

 the paraphyses of certain species, and found thatt their presence greatly 

 depends upon some special condition of the fungus. " I find them con- 

 stantly present with the uredospores of Puccinia perplexans, Plow., when 

 these have arisen, not directly, but rather at a considerable distance from 

 the aecidiospores. On the other hand, when the uredo arises directly 

 from the aecidiospore, they are hardly present at all ; this looks very much 

 as if they were an indication of exhaustion of vital energy on the part of 

 the fuingus, which _was combated by protective efforts on the part of the 

 parasite in conserving those spores which it does produce, but when full 

 of vigour and fresh from the aecidiospore it is less careful of its spores. 

 When it begins to feel the, effect of exhaustion, and is unable to develop 

 such energetic spores, it takes more care of those which are produced." 



Or it may be that when the fungus begins to feel exhausted, it is 

 unable to develop 1 so many spores, and barren protective filamesnits take the 

 place of those which would normally produce spores. If the paraphyses 

 serve to prevent excessive evaporation, then it would follow that in the 

 early spring, when there is little need for protection on this account, tEere 

 would be little use for them ; but towards the summer, when the air is 



