May 1907] An Apple Rot Due to Volutella 95 



While the decayed portions are softer than the healthy, this 

 is in no sense a wet rot, the softness being due to a spongy 

 dryness rather than to a watery dissolution. Upon microscopic 

 examination the cells of the old, dark, diseased portion of the 

 apple are found to be filled with a tangled mass of black or 

 dark brown fungous threads which are richly septate and much 

 branched ( Fig. i ) . In thickness they vary from 5 to 7 ju. in 

 the older portions. In the newly invaded cells the mycelium is 

 usually only about 2 ju. thick and is colorless. 



As the spot ages the mycelium develops more abundantly in 

 a few layers of cells next to the cuticle, particularly immediately 

 under the cuticle. From this sub-cuticular. layer of tangled my- 

 celium there develops a cushion of hyphae which are arranged 

 parallel and stand upright, perpendicular to the substratum. 

 These hyphae are quite uniform in thickness and regular in 

 arrangement, composed of short, rectangular cells (Fig. 2). 

 These upright hyphae increase in length, rupture the cuticle and 

 develop the tubercular mass, "sporodochium," characteristic of 

 the order Tuberculariales. The sporodochia attain a height of 

 100 to 125 /x and a diameter nearly twice as great. About 

 midway from base to top of the sporodochium the hyphae be- 

 come narrower and the setae have their insertion. The setae 

 develop directly from hyphae which stand amid sporophores and 

 are indistinguishable from them, their only point of difference 

 being that the setigerous hyphae broaden out at the end and 

 develop into typical setae while the sporogenous proceed to spore 

 development. Each setum is produced from the tip of a single 

 hypha (Fig. 3). The setae are from 100 to 400/* long, taper- 

 ing from the base to tip. At base they are 5 to 8 /u. broad 

 and bear from 2 to 5 septae (Fig. 4). 



At the upper end of the erect fuscous or black hyphae. 

 which constitute the sporodochium is a simple, slender hyaline 

 stalk ''condiophore'' from 25 to 35 ju, by 3 //. which bears 

 the spore. The conidiophores together constitute the outermost 

 layer of the sporodochium. The spores are produced acrogen- 

 ously. being cut off from the tips of the conidiophore by con- 

 striction of the fertile hyphae. 



The spores are oblong-fusoid to falcate-fusoid with acute 

 ends (Fig. 5) hyaline or very slightly olivaceous, continuous, 

 though with the low power of the microscope they often appear 

 uniseptate ov/ing to peculiarities of the protoplasm in this region. 

 They measure from 17 to 23 /a long by 2.5 to 3.5 m broad. 



Placed in apple agar in hanging drop cultures they germin- 

 ate in about three hours ; at first by a single liyphal thread near 

 one end of the spore, but later other points of germination can 

 be seen. When germination begins the spores become very 

 coarsely granular. The granules become fewer in number and 

 larger as germination proceeds. Later by the migration of the 



