704 
Journal of Agricultural Research v 0 i. xxvn, no . 9 
Measurements of conidia from spots on apple leaves. (Arlington 
Experiment Farm, Rosslyn, Va., September, 1921): 
Average. 
1- septate (2 per cent), 16x9 ..16 x 9 
2- septate (io per cent), 19 to 22 x 8 to 13. ... 21x11 
3- septate (56 per cent), 20 to 29 x 8 to 13.25 x 12 
4- septate (22 per cent), 27 to 38 x 9 to 15. 32 x 13 
5- septate (10 per cent), 42 to 46 x 9 to 15.43 x 13 
With longitudinal septation (78 per cent) width n to 14. 13 
Without longitudinal septation (22 per cent) width 8 to 13. 10 
Conidiophores (isthmi), 2 to 30 x 3 to 5. 6x4 
Number of septa for all the conidia. 3. 28 
Dimensions of all the conidia. 28x12 
Measurements of conidia from a nine-day-old culture on a corn-meal 
agar plate (fungus newly isolated from spots on apple leaves): 
Average. 
1- septate (2 per cent), 13 x 7.13 x 7 
2- septate (18 per cent), 17 to 21 x 8 to 13.19 x 11 
3- septate (46 per cent), 21 to 29 x 9 to 13.24 x 11 
4- septate (22 per cent), 29 to 37 x 9 to 14.34 x 12 
5- septate (6 per cent), 34 to 38 x 8 to 13.36 x 11 
6- septate (6 per centj, 36 to 46 x 10 to 13.41 x 12 
With longitudinal septation (76 per cent), width 10 to 14. 12 
Without longitudinal septation (24 per cent), width 7 to n. 9 
Conidiphores (isthmi) 2 to 12 x 2 to 5. 5x4 
Number of septa of all the conidia.. 3. 30 
Dimensions of all the conidia.27X 11 
Measurements of conidia from a nine-day-old culture on a corn-meal 
agar plate (fungus isolated from apple leaves and grown in artificial 
culture about one year): 
Average. 
1- septate (8 per cent), i3toi5x8to9. 14x8 
2- septate (20 per cent), 17 to 25 x 8 to 13.20 x 10 
3- septate (56 per cent), 20 to 29 x 8 to 13. 25x11 
4- septate (8 per cent), 25 to 34 x 9 to 12.30 x 11 
5- septate (4 per cent), 34 x 11 to 12...34 x 12 
6- septate (4 per cent), 42 x 9 to 13. 42x11 
With longitudinal septation, 58 per cent, width 9 to 13. 12 
Without longitudinal septation, 42 per cent, width 8 to 11. 9 
Conidiophores (isthmi), 3 to 12 x 3 to 5. 5x4 
Number of septa for all the conidia. 2.92 
Dimensions of all the conidia.24 x 11 
Alternaria Mali, in addition to causing enlargements of dead spots on 
apple leaves, is capable of infecting the fruit. It is reported by Reed 
and Crabill (15) as causing a soft rot of the fruit of the York Imperial 
variety of apple following “skin crack” and “York spot.” 
Wolf (21), Longyear (13), Clinton (5), Stakman and Rose (19), and 
Cook and Martin (6) reported on species of Alternaria isolated from apple 
fruits, but gave no descriptions of them. Longyear’s drawings show that 
his fungus greatly resembles and is possibly identical with Alternaria 
mali. Longyear also found the fungus growing on the leaves and sprouts 
of the pear. 
Mclnnes ( 14) and Home (10) give descriptions of the species of Alter¬ 
naria which they found in dead spots on apple fruits. Of these species, 
Alternaria pomicola Home has much larger spores than Alternaria mali. 
The Alternaria tenuis variety X of Mclnnes resembles Alternaria mali 
much more closely but has somewhat larger conidia. 
