8 CLASS-BOOK OF BOTANY. 
ed j ] 
The fourth whorl of floral leaves, left aftex be as a 
petals, and stamens have been removed, consists - ie eee 
small green carpels. Remove one of these with the p 
Fig. 4. Pistil of Buttercup; show- 
ing the thalamus or receptacle Fig. 5. Carpel of Buttercup 
underneath (mag.). (mag.) ; st=stigma, 
a knife-blade or needle, and examine it under the lens. It is 
found to be a short pod-like body, with the lower portion con- 
siderably swollen and bulged, and the upper portion slightly 
hooked. Notice that the apex of this upper portion appears 
to be formed of small damp projecting cells, or papilla. This 
portion is called the stigma, and its papillose viscid (sticky) 
surface enables it to catch and retain any pollen-grains which 
come in contact with it. Now make a longitudinal section 
through the carpel. If you have a very sharp knife—as you 
ought to have—this can be done, with a little practice, by 
holding the carpel between the finger and thumb ; or you may 
take a little bit of the pith of an elder and, making a slit in it, 
place the carpel into it and cut the sections in the way 
desired. You wil find that the carpel is hollow, and has 
attached to the lower end of the swollen portion, or ovary, a 
rudimentary seed or ovule. The narrower portion of the 
carpel above the ovary, and which bears the stigma, is called 
the style; it is not, however, well-defined in the buttercup, 
and you will meet with much better examples in some of the 
other plants to be examined later on. Notice now that all 
the carpels are quite separate from one another; we there- 
fore say their cohesion is apocarpous,* and from being fas- 
tened above the other parts of the flower their adhesion is 
said to be superior. 
It would not be an easy matter to prove directly that the 
stamens and carpels of a buttercup are modified leaves of 
some kind, and yet if you examine the common “‘Bachelor’s 
Button of the garden you will find just a buttercup in which 
all the stamens and most of or all the carpels have turned 
into petals. However, we shall probably come on examples 
of other flowers which will help us to prove this fact more 
satisfactorily, 
“Gr. apo, from; karpos, a fruit. 
