80 THE NATURE-STUDY OF PLANTS 
seeds must be kept at an appropriate temperature. 
In order to obtain some evidence of my own I 
experimented one summer with seeds of various 
sorts and sizes, and I found that with the smaller 
seeds of the Pink and Stock, which by the way are 
also flat, the radicle starts all right on a moist soil, 
although it may fail to find a soft spot or a tiny crevice 
into which its tip can grow. 
If it be lying loose on the surface and does not 
produce roothairs in sufficient numbers to fix it in the 
soil, it cannot get the requisite purchase, and sooner 
or later it will wither and die. 
Even if it succeeds in finding a friendly crack and 
in inserting the tip, the next difficulty is with the 
cotyledons, and for many but not all seeds it is by no 
means easy to get them free from the coat unless the 
latter be fixed. ; 
Some seem to get on, provided the radicle manages 
its business properly, and especially those of the 
family to which the Stock belongs, and of which 
Mustard and Cress are familiar examples. If we 
sow seeds of either of these two, as is commonly done, 
on a piece of damp flannel we shall be able to see how 
the roothairs fix the radicle and how the cotyledons 
divest themselves of the seed-coat, whereas others, 
such as Violets and Convolvuluses in addition to the 
Pinks, come off very badly indeed in the struggle. 
Now, while the radicle is of course entirely indis- 
pensable, the cotyledons are so important for the ade- 
quate nutrition of the seedling that if we cut them 
off it perishes inevitably and if we remove only one 
the chances of its survival to maturity are jeopardized. 
As far as getting free from the seed-coat is concerned, 
I need hardly add that I am speaking only of those 
