ON AN OPENING IN SOME LEGUMES. 121 
pod, became soon so considerably reduced. in.size as to leave a large 
air-space. at first imagined that the water was lost 
by transpiration through the pod itself, but eloser 
scrutiny revealed another agency. In the Fada vul- 
garis, when the seed is mature, a small oval opening 
appears close to the proximal extremity of the ventral 
suture of the pod (vide Fig. 1). Through this open- 
ing evaporation of water from the seeds takes place 
without necessitating the dehiscence of the pod and 
the sheddiug of the seeds. 
It becomes a matter of interest to ascertain whether 
a similar opening occurs in other legumes. The pod 
of some varieties of Phaseolus vulgaris showed traces 
only of such an opening; but in Phaseolus pisiformis, 
a Senegal species, a minute orifice occurs (vide Fig. 2). 
A remarkable approach to this arrangement is seen in 
Diphysa Carthaginiensis, Jacq. In the pod of this Fig. 2. 
plant the vascular tissue immediately on leaving the peduncle on the 
ventral aspect, separates into two bundles, and interposed between 
them lies a tract of cellular tissue, indicating the site of a possible 
opening (vide Fig. 3). But in a species of Acacia, from Panama, the 
b 
Fig. 4. 
Fig 3. — 
opening is remarkably distinct (vide Fig. 4). In some of the speci 
mens of the pod of this plant (possibly 4. concinna) insects, finding 
this natural opening the easiest point of attack, had enlarged it to 
make their way into the pod. Fig. 4 b is a front view of the opening 
