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Parasitic Aphelenchi 
diseased patches in search of fresh nourishment for itself and its progeny; 
eggs are found laid only in healthy tissue, consequently the gravid female 
has the greatest impulse to travel. 
Adults and larvae reach the soil by the fall of the diseased leaves, bringing 
the life cycle of the race 1 to the resting stage in the soil. 
B. The besting stage in the soil. 
Marcinowski (1910) asserts that the parasitic Aphelenchi can live only for 
a very short period in the soil, in fact that they only enter the soil in order to 
pass directly from a fallen leaf to a new host plant. 
She placed portions of infected leaves on the earth of a pot, which was kept damp, and 
examined the earth from the second week onward—result negative. On the other hand, 
earth in which an infected Begonia had grown, proved infectious when placed on leaves of 
begonias. 
Ritzema Bos (1892) showed that Tylenchus dipsaci can persist in the soil 
only on the surface, where it can undergo partial drying, and so enter a dor¬ 
mant condition. I found that adult A. phyllophagus can live actively in 
water for at least six days. Early death in damp soil may be due to mycosis. 
Molz (1909) apparently believes that A. phyllophagus resides in the soil. 
I have made the following observations to test the power of survival in 
earth: 
Portions of infected leaves of Chrysanthemum and Lomaria ciliata were placed on earth 
in pots, which were watered daily, the surface of which, however, remained dry except for 
a period not exceeding two minutes each day. On the 1th and 9th days many adults, male 
and female, were found on the surface of the leaf fragments, a few actually in their tissues. 
On the 1 6th, 11th, 20 th and 4:9th days the surface layer of earth was examined. It was 
quite dry at the time, and had been at a temperature below the freezing point at night. 
Adult Aphelenchi were found in large numbers in a dormant condition, but they resumed 
activity after immersion in water. Larvae and eggs were looked for on the 46th day, but 
were not found. In earth taken from 10-15 mm. below the surface no Aphelenchi were found. 
We can therefore conclude that A. phyllophagus and olesistus reaching the 
soil in fallen leaves, can live there for at least 46 days. Like T. dipsaci, they 
collect on the surface of the earth, where they suffer partial desiccation, and 
pass into a condition of suspended vitality. In the case of T. dipsaci, it is 
the larvae only which survive in this manner, while in Aphelenchus on the 
contrary the adults survive, and it is doubtful whether the larvae do so (they 
probably grow to adults before abandoning the fallen leaves). 
1 It should be clearly realised that the life cycle in Aphelenchus and T. dipsaci is that of the 
race, while in T. tritici it is that of the individual; in other words in the cycle from (a) the definitive 
habitat, through (b) the resting stage in the earth, and (c) the stage of immigration, many genera¬ 
tions are completed in the former, only one generation in the latter; also many cycles can be com¬ 
pleted in one year in the former, only one in the latter. Hence the enormously greater power of 
multiplication in the former than in the latter. 
