Morphology and Life-History 3 



call at once the appendages of some species of ErysipJie (see 

 Woronin, Beitr. Morph. Phys. Pilz. 2: 3, //. 2. f, 7,8). We 

 must remember, too, that in Erysiphe and Sphacrotheca the appen- 

 dages are often obsolete. The function of this ''secondary my- 

 celium" is, generally, to secure the attachment of the perithccium 



iph 



have ap- 



parently been specially modified for purposes of distribution. 



Harper (161) has some interesting remarks on the subject of 

 the relationship of the Erysiphaceae. 



Morphology and Life-History, 



The ordinary vegetative mycelium consists of very numerous, 

 delicate, white or colorless septate hyphae, frequently branched and 

 more or less densely interwoven. The septa divide the hyphae into 

 rather long cells, which according to Harper (161) contain, as a 

 rule, only one nucleus, although cases where two to four nuclei occur 

 are not uncommon. In all the genera except PJiyllactinia, the hy- 

 phae of the vegetative mycelium produce haustoria at inter\^als 

 which pierce the cuticle and swell out into a bladder-hke form in the 

 epidermal cells. These haustoria serve both to attach the fungus to 

 its host and to draw nourishment from it. The haustorium is 

 very narrow at the point where it pierces the cell-wall, and is fre- 

 quently, at its entrance into the interior of the epidermal cell, sur- 

 rounded by a sheath-like process proceeding from the cell- wall 

 (see Fig. 155). According to Harper (161) each haustorium con- 

 tains a single nucleus, situated towards the end, or in the middle 

 of the bladder-like swelling or sac. This sac applies itself closely 

 to the nucleus of the epidermal cell, and at length is completely 

 surrounded by this nucleus, which gradually becomes disorgan- 

 ized, forming a thick granular coat round the haustorium. Finally, 

 the whole of the protoplasmic content of the host cell becomes 

 disorganized. The haustoria originate from the mycelium in three 



different ways ; they may spring direct from the under surface of 

 a hypha at a point where it is closely applied to the surface of the 

 host plant, and at once pierce the cuticle. These are termed haustoria 

 exappendiculafa ; or at certain places, at the side of the hypha, 

 flattened semicircular processes appear, usually small, not exceed- 

 ing in wadth the diameter of the hypha, and from the under sur- 



