1879. ] Cross-Fertilization in Flowers. 5 
described. We have, therefore, the stigma shut up with the pol- 
len in the same cell. “ A capital arrangement for se/(fertiliza- 
tion,” one says. Nay, not too fast! The stigma is composed of 
two fleshy lobes, its receiving surface being on their inner surface. 
And they are closed firmly together, so that the end of the pistil 
looks like a closed mouth with its lips firmly pressed together. 
| With its bristly collar it reminds one of Jack-in-a-box, with an 
unusually “ stiff upper lip.” 
This combined pistil and stamens is S-shaped, and when the 
flower opens, it springs through the slit on the upper side of the 
corolla and stands with the tip of the pollen-cell just behind the 
upper lip of the corolla, vide Fig. 7 a. The front view of the 
same is given in Fig. 7 6. Sometimes there is no trace of the 
stamens seen from the front; but if an insect tries to enter, the 
slit between the petals opens, the hairs of the anthers strike his 
back, and as he forces his way in, they 
produce a jarring of the pollen-cell which 
freely sprinkles the pollen upon him. 
As the pollen escapes it is kept up to 
the pore by the pressure caused by the 
gradual lengthening of the style. The 
hairy collar acting like a swab, sweeps the 
cell clean. When all the pollen is gone, 
the style, continuing its growth, pushes the 
through between the upper petals. The 
end of the style then comes downward, Fie. 8.— Zobelia aspir 
the lips of the stigma open and roll back ica in the pistillafe np oe a, 
as though turning inside out. This ex- “¢f Mec aai erer Spa 
poses the whole surface of the stigma to be stigma, enlarge ea 
covered with pollen from the back of the first insect which comes 
from a flower discharging pollen. So the cross-fertilization is 
beautifully accomplished. | 
These entertaining structures present some very suggestive — 
ideas. We are impressed with the importance of cross-fertiliza- 
tion in the economy of nature, but why it should be of any 
advantage who can tell? We readily see that in several of these _ 
cases cross-fertilization between flowers upon different roots is likely 
to be quite rare. In Martynia such fertilization may be quite — 
frequent, as there are comparatively few flowers open at once, but 
