36 
Garden Work 
pores (stomata), which are surrounded by tiny cells called 
guard cells. It is through these stomata that the plant 
breathes most actively. These stomata also take in a 
large proportion of food substance from the air in the 
shape of a gas called carbon dioxide (CO z ). They also 
give off the superfluous moisture which has been taken 
up by the roots. The guard cells of each stoma are 
affected by the light. In intense sunlight they open 
widely, but as darkness 
comes on they partially 
close. The atmosphere, 
when saturated with mois- 
ture, also has the effect of 
partially closing them. 
The stomata are more 
abundant on the under 
side of the leaves. Here 
again Nature has taken 
precautions for the wel- 
fare of the plant, as in 
this position there is less fear of these stomata being 
choked with dust than if they had been on the upper 
side of the leaf. 
Underneath the epidermis we get the layers of cells 
which are filled with coloured matter called chlorophyll. 
This substance is usually of a green colour, although it 
varies, as can be seen from that of the Beetroot, Copper 
Beech, &c. Now it is in these layers, in the chlorophyll 
corpuscles of these layers, under the action of sunlight, 
that all the food of the plant is manufactured. The parts 
which are taken up from the soil by the roots unite with 
Stomata. Surface view of part of Frond of Fern 
