50 



BULLETIN 121, U. S. DEPARTMENT OP AGRICULTURE. 



286) . The lateral walls are thin except for a rodlike thickening extend- 

 ing from base to apex of each cell. The processes of fermentation 

 and washing remove all of this cell layer except these rodlike thick- 

 enings, most of which remain as cellulose hairs (fig. 15). These 

 hairs become closely appressed to the seed when the latter is dry 

 and may protect adhering spores or appressoria from extreme 

 desiccation. Furthermore, since the fungus may be present in the 

 adhering fragments of fruit tissue it is evident that in this form 

 desiccation could be more readily endured. 



It is scarcely believed at present that the fungus will survive an 

 additional year's storage, and hence it is only reasonable to main- 

 tain that the disease is introduced only with seed planted the year 

 after it is harvested. This is an important consideration, since in 

 practice much of the cucumber and melon seed is more than a year 



old when used. Cucum- 

 ber seed is known to re- 

 main viable from two 

 to six years, and many 

 growers prefer old seed. 



POSSIBILITY OP INTERNAL CAR- 

 RIAGE OF MYCELIUM. 



Fig. 15.- 



-Cross section through the seed coat of a cucumber seed, 

 showing cellulose rods, or "hairs." 



There is also the pos- 

 sibility of internal car- 

 riage of dormant myce- 

 lium within the seed. 

 Eriksson (16, p. 127), 

 after failing to find my- 

 celium in supposedly 

 infected seed, advances 

 his my ooplasm theory to account for anthracnose carriage in cucum- 

 ber seed. The depth of fruit lesions as observed on seed cucumbers 

 and watermelons suggests that seed infection may occur previous to 

 seed extraction. From observations made upon seed cucumbers col- 

 lected in October, 1917, it appears that there may be considerable 

 opportunity for the internal infection of seed. Coalescent lesions 

 were found penetrating the placentae as far as the seed, and in some 

 instances the gelatinous capsules were decomposed and the funiculi 

 rotted off at the points of attachment to the seeds. 



Samples of seed removed from beneath such lesions were tested 

 in two ways for the presence of the anthracnose fungus. The seeds 

 were sterilized in mercuric chlorid, 1 to 1,000, for five minutes, washed 

 in sterile water, and some were planted intact in poured plates of 2 

 per cent dextrose agar. From others the embryos were aseptically 

 removed and planted in similar plates. Tests were made on Novem- 

 ber 4 and December 14. In 87 seeds tested by the former method 

 and 90 by the latter no trace of the anthracnose fungus was obtained. 



