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of about 6 mM. In transverse section it is almost round, 
but on account of the ten prominent ribs, running over 
the whole length, it obtains the form of a decagon. In 
the middle it has its greatest diameter. 
The seed is built up of a testa and a central part the 
nucellus. 
The testa forms a ribbed envelopment, at its lower part 
tightly closed, and concrescent with the nucellus, but in 
its apical region it becomes free and there it is divided 
into ten arms or tentacles, forming a rina around the 
nucellar apex. The ribs are less visible at the base, but 
higher they become more and more prominent, till at last 
they are continued in the entirely free tentacles. In these 
tentacles, which take up one-third of the whole length of 
the seed, Physostoma has a distinctive character, and is 
clearly distinguished from the other seeds, where at best, 
as in Lagenostoma and Sphaerostoma, the micropylar tube 
is formed by a ring of loculi, the canopy, which probably 
indicates an original ring of arms or lobes, but which are 
now concrescent and form a closed tube. 
Very characteristic too is the dense covering of the ribs 
and the abaxial portion of the tentacles with long club- 
shaped hairs. They attain a length of about 0,5 mM. near 
the median line of the rib. Undoubtediy they formed a 
thick clothing of the seed in its life-time. 
The testa or integument is formed of a thinwalled tissue, 
which gives no indication of fibres or sclerotic cells; on 
the whole the tissue is very delicate, probably in connec- 
tion with the dense hair-covering. 
The vascular system is like that of Lagenostoma Lomaxi. 
At the base of the seed a vascular strand enters the 
chalaza and is divided into ten bundles, running through 
the body of the ribs, on a level with the intermediate 
grooves, and which are continued in the tentacles. 
The nucellus is concrescent for two-thirds of its length 
