180 
JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
with Cress. The seeds were laid on the surface of the soil 
and just covered with a thin layer of the same soil, or in the 
case of the rammed clay, the pebbles, and the burnt clay with 
a thin covering of damp sand, which, as subsequent experience 
showed, would have been better omitted. The pots were 
placed in an open frame in the garden. 
On the same day seeds of Mustard and of Cress were 
sown on plates of charcoal (8), and on slabs of glass (9), the 
seeds being covered in the latter case with cotton-wool kept 
moist. The three last-mentioned sets of seeds were placed in 
a cupboard in a room warmed in the daytime by a fire. 
On the 3rd of February, the seeds on the charcoal and 
on the glass were examined, with the following results :— 
(8) Charcoal. Mustard seedlings, February 3rd, average height 
of seedlings 10 centimetres, of tigellum 7 4 —8, of radicle 2 —3 
centimetres (a few root-hairs). Cress seedlings, average height 
7—8 centimetres, of tigellum 5, of radicle 2 —3 centimetres. 
(9) Glass. Mustard, average height 4— 5 centimetres, of tigellum 
2—3, of radicle —2 centimetres. (Eoot-hairs extremely 
abundant and very fine, forming a dense cobweb-like leash or 
net work.) Cress, average height 3—4 centimetres, of tigellum 
1-|—2, of radicle 2— 2% centimetres. (Root-hairs of the same 
general character as in the case of the Mustard but less dense.) 
The seedlings in one set of pots were examined on 
February 16th, and the following appearances noted; the 
measurements being taken from the seedlings near the centre 
of each pot and in such a way as to give a fair average of the 
entire height, of the height of the tigellum and of that of the 
radicle. The measurements must, however, be looked on as 
approximative only :— 
(1.) Rammed Clay. Mustard, average height 8—9, length of 
tigellum 3—4, of radicle 4—5 centimetres. Cress, average height 
3, length of tigellum 1, of radicle 2 centimetres. 
In neither case were there many root-hairs, all the time 
the radicles remained in contact with the soil. Despite the 
thickness and tenacity of the clay, the radicles penetrated it to 
reach the sides of the pot; having done so, they produced 
an abundance of root-hairs. 
In the subsequent paragraphs, in order to save repetition, the 
words tigellum and radicle are omitted; but it will be under- 
