186 
JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY, 
stunted and withered, so that it is to be presumed that they did 
not get then’ fair share of moisture, which by some accident was 
concentrated on that half containing the Cress. 
In number 6 (rotten leaves), the conditions were very favour¬ 
able except in the matter of penetration, the tough leaves 
offering a considerable obstacle. Still, the moisture and the 
decaying vegetable matter furnished a relative abundance of 
food, as is seen by the high average vigour. The length of root 
was relatively small, but the proportion of root-hairs was large. 
In No. 7 (road scrapings) the conditions were also favourable, 
the soil was readily permeable to water and air, readily laid hold 
of by the roots, and no doubt contained available plant food. The 
general result was an even growth, and a high average develop¬ 
ment of all parts of the seedling plant. 
With reference to the production of root-hairs, some further 
remarks may be made arising out of these experiments. The 
length of the radicle offers no guide to the number of root-hairs. 
If the food is within a short distance there is no need for the 
roots to travel far, and they throw out their feeders where the 
food is to be obtained. Wherever the soil is light and porous, 
there the root-hairs may be expected to be most abundant, and 
wherever there is a thin film of water investing a stone, or the 
side of a porous flower pot, or a plate of glass, there the root 
hairs abound. Where the opposite conditions prevail, there the 
production of root-hairs is relatively small. 
The variations in the total length of the seedlings and of the 
radicle are easily explained by the circumstances of growth. 
On the other hand, the comparative uniformity in the height of 
the tigellum may perhaps be explained by the fact that the 
office of this part of the plant is simply to uplift the seed leaves 
above the surface, and this done, there is no further need for it 
to elongate. Koot-hairs are never, I believe, produced from it. 
The great length of the tigellum in pot No. 6 (rotten leaves), 
both absolutely and relatively, is noteworthy. It occurred in 
the Mustard seedlings as well as in the Cress, but I am not able 
to suggest an explanation of the phenomenon. 
