221 
SrxtH.—Jn most cases the highest germination percentages in composites are obtained 
from surface planting in leaf mold. 
Arctium is the exception to this statement also. By surface sowing 
upon leaf mold, under the three conditions of moisture, Arctium gave an 
average germination percentage of 22.2 per cent. In sandy loam, where 
the achenes were covered by sifting earth over them, the percentage rose 
to 93.3 per cent. In all other cases, however, the leaf mold gave much the 
larger per cent. This was especially marked in the case of Cnicus lanceo- 
latus, in which in sandy loam the percentage was 12.5, while in leaf mold 
the average percentage was 89, rising in one case to 100 per cent. The 
experiments indicate strongly that successful germination in composites 
is more closely dependent upon the character of the soil than is the case 
in the majority of our native plants. In other words, their soil range is 
so narrow that a slight modification in its character may practically pre- 
vent germination of the achenes and thus very effectually limit distri- 
bution. 
SeveNntTH.— The water content of the soil does not (so far as is indicated by these’ 
experiments), affect the germination percentage to the degree that might have been ex- 
pected. 
While differences in the water content of the soil affects the seedlings 
in a marked way, germination is unaffected under a wide range in water: 
content of the soil. In extreme cases, some forms show marked varia- 
tions. Arctium, for example, which gives a germination percentage of 
93.3 under ordinary soil moisture conditions, falls to 3.3 per cent. in the 
case of extreme dryness. Cnicus lanceolatus, on the contrary, rises to 100 
per cent. in extremely dry soil. In the forms studied the highest per- 
centage of germination is found under moderately moist conditions, and 
the lowest under extremely dry conditions, save in the case of Cnicus 
lanceolatus, where the reverse seems to be true. Extreme soil moisture in 
many cases leads to the moulding of the achenes. 
A careful dissection of material used in these experiments showed 
that there was nothing in the character of the achenes themselves to 
which this low germination percentage could be attributed. The material 
was collected with care expressly for these experiments, and dissection 
demonstrated well formed embryos in more than 80 per cent. of the 
achenes examined.? I am, therefore, led to believe the low germination 
2? The achenes thus examined were taken from the portion of the head indicated in con- 
clusion three, swpra. 
