HOW TO DISSECT A FLOWED. 
143 
coloured corolla (which hi this instance is the coloured portion 
of the flower). The green cup, or calyx, is five-angled (fig. 1), 
and surmounted by five long narrow sharp-pointed teeth. In 
some other flowers — the strawberry, for instance — this calyx is 
composed of five little green leaves ; but in the primrose the 
edges of these five leaves are united into a tube, with no other 
indication of the five leaves of which it is theoretically com- 
posed than the five sharp teeth, which are the apices of the 
leaves, and the five ridges (fig. 2, section) which correspond 
to the midrib of ordinary leaves. If these leaves of the calyx 
had been divided so as to have the appearance of five separate 
leaves, each of these would have been a sepal ; but, as all are 
united, they constitute a monosepalous, or one-sepaled calyx. 
In some flowers the sepals are all united at their edges into 
a monosepalous calyx. In others the sepals are distinct and 
form a polysepalous calyx. The primrose has a monosepalous 
calyx. 
If we observe the flattened expanded surface of the flower, 
we can count five somewhat heart-shaped flower-leaves, which 
are notched at the outer margin, and united at the base, with 
what appears to be a little hole in the centre (fig. 3). If we 
fold together these flower-leaves, and, holding the stalk of the 
flower firmly in our left hand, draw from it the flower-leaves 
between the thumb and finger of our right hand, we shall be 
able to remove the flower-leaves, or corolla, in one piece from 
the calyx. We have now a cylindrical tube of an inch in length 
(fig. 4), with five lobes spreading nearly at right angles to it ; 
and the hole in the centre, seen when looking down upon the 
flower, was the mouth of this tube. Had each of the five flower- 
leaves been separate, as in the strawberry, we could have plucked 
them off one by one, and each would have been called a petal ; 
but as all are united together at the base, the primrose has a 
monopetal ous corolla. It should also he observed that not only 
are the petals united, but also prolonged into a tube at the base, 
which is not the case in all corollas having the petals united. 
In some flowers the petals are all united at the base into 
a monopetalous corolla. In others the petals are distinct, and 
form a polypetalous corolla. The primrose has a monopetalous 
corolla. 
We must now for the first time seek the assistance of a knife. 
A sharp penknife will answer the purpose ; but one of the small 
knives with a sharp point sold by opticians for the use of 
microscopists is better. Insert the point of the knife at the 
bottom of the tube of the corolla, just drawn from the calyx, 
and cut it open through its whole length. Lay the corolla upon 
a piece of sheet cork, about three inches square. Open the tube 
with a dissecting needle (any needle with the head fixed firmly 
