NOTES ON ROOT-HAIRS AND ROOT GROWTH. 
181 
stood that the first brace of figures refers to the total average 
height, the second to the length of the tigellum,the third to that 
of the radicle. 
(2.) Pebbles.— Mustard, 7— 8, 2£, 5 —6 centimetres. Cress, 
4—6, 1J, 4 centimetres. 
The Mustard, produced, numerous root-hairs when the radicles 
penetrated the smaller interstices between the stones. The 
Cress under the same circumstances produced very few. 
(3.) Ballast.— -Mustard, 9—10, 2—8, and 6—7 centimetres. 
Cress, 5—6, 1|—2, and 2£—3J centimetres. 
In the Mustard dense root-hairs were observed where the roots 
came into contact with the sand by which the lumps of ballast 
were covered; in the Cress they were much less abundant. 
(4.) Garden Soil. —Mustard, 10—12, 3—4, and 7—9 cen¬ 
timetres. Cress, 5—6, —2, and 4—4£ centimetres. 
In this instance the roots descended vertically into the soil. 
In the case of the Mustard there was a production of a dense 
mass of root-hairs to which the soil adhered, while in the case 
of the Cress the hairs were very much less numerous. 
(5.) Flannel.— Mustard, 6—7, 2-J-, and 4—5 centimetres. 
Cress, 3, 1, and 2 centimetres. 
The flannel was covered with a thin layer of sand, in passing 
through which the radicles of the Mustard developed a few 
root-hairs, while none, or only a few and those very small, 
were formed while the roots were traversing the flannel. Very 
few hairs were produced on the roots of the Cress. 
(6.) Decayed Leaves.— -Mustard, 9—10, 4, and 5 centimetres. 
Cress, 5, 2—3, and 3 centimetres. 
In the case of the Mustard the radicles were very densely 
clothed with root-hairs all the way up from near the apex. 
The Cress had comparatively few hairs. 
(7.) Road Sand.— Mustard, 9—10,2J—3, and6— 7 centimetres. 
Cress 6, 2, and 4 centimetres. 
Upper end of radicle of Mustard covered with a dense mass 
of hairs to which the soil was adherent; tip nude. The Cress 
presented like appearances but less in degree. 
On the 3rd of March the second set of seedlings were examined 
and the following notes taken : — 
(1.) Bammed Clay. 
N 
