Connection of the Sporocarp in Marsilia Polycarpa. 205 
is somewhat flattened, and at the apex the protoxylem elements are 
found, bordering on a canal probably formed by the disintegration 
of the earliest tracheids (Fig. 1). 
As the point of attachment of the stalk of the sporocarp is 
approached, the vascular strand is found to become rather extended 
towards one side. One arm of the V stretches out (Fig. 2), and at 
this point the air-spaces disappear, and the band of sclerenchyma 
broadens and is practically continuous with the endodermis. The 
parenchyma of the pericycle now begins to intrude, and the vascular 
bundle of the sporocarp is nipped off from the lengthened arm of 
the xylem strand. The pericycle is followed by the endodermis 
and the small strand is thus separated from the main strand of the 
petiole by an intrusion of parenchyma (Fig. 3). After the bundle of 
the sporocarp has been nipped off, the arm of the V on that side 
remains elongated, and the vascular strand of the sporocarp next in 
succession comes off in exactly the same manner as the first sporo¬ 
carp. The arm of the V elongates even more than in the first case, 
and the margin separates off to form the bundle of the stalk. This 
occurs in the succeeding sporocarps. 
At the distal end of the leaf, four wedge-shaped leaflets are 
present. Sections were cut from about below the insertion of 
the leaflets on the petiole, through the insertion of the leaflets and 
through the leaflets themselves. In the petiole itself the cross 
section is similar to that of the petiole below the attachment of the 
sporocarps. The vascular strand is marked off by a well-defined 
endodermis, and the single leaf-trace is V-shaped (Fig. 4). In the 
sections nearer the point of insertion of the leaflets, the petiole is 
found to have increased in diameter and the arms of the strand 
become somewhat flattened. The xylem shows signs of breaking 
up into three separate groups (Fig. 5), each group having a 
tendency to turn out at the two ends. By this time the whole 
section has assumed the shape of the three xylem-groups (Fig. 6), 
and the pericycle creeps in between the out-turned ends. Following 
the pericycle is the endodermis, and a group of xylem elements, 
surrounded by phloem and endodermis, occupies each of the three 
lobes of the petiole. These three lobes finally become separate 
(Fig. 7); but before separation, the single bundles of the lateral 
lobes have divided into two, while the bundle of the median lobe 
also begins to divide. As soon as the bundle of the median lobe has 
divided into two by splitting across (Fig. 8), a constriction appears 
above the split and gradually deepens until it divides the lobe into 
