288 THE AMERICAN MONTHLY [Nov 
the banana petiole one fourth smaller than the natural size. 
Fig. 2 represents a short piece of a section cut down- 
wards from the line aa of Fig. 1. Fig. 3 gives a por- 
tion of an ethmoid diaphragm magnified about fifty times. 
Fig. 4 is a tranverse section, of one half the actual size 
of a sheath, taken a little below where it narrows and 
bends out to become the petiole proper. These sheaths 
extend down to the ground and together form the body 
of the plant. Air passages with ethmoids also make up 
4 ) as 
ive tiers of flowers and are thrown off, one by one, as the 
fruit develops. Fig. 5 shows a cross section of one them 
enlarged five times, the upper part being the outside. 
The diaphragms, as shown in fig. 2, are hardly two 
millimetres apart. Therefore if we examine with the mi- 
croscope several successive cross slices of a petiole, we 
shall be sure to find among them some that have one or 
more of the diaphragms in place. Or we may split off 
the side as in fig. 2, so as to expose the interior, and 
a i ee 
