592 Affour tit and La Riviere . 
many gradations between those two regular kinds, i. e. the two- and three- 
ribbed types, but there were also other forms, still undescribed, as far as we 
are aware. 
Whilst nearly half the number were two-angled, even these were 
not quite regular in form ; three kinds of them could be distinguished, 
though the differences between them were rather slight. In most cases the 
sides were equally curved, as in the drawings of Eichler and of Saporta and 
Marion, and as in our own Fig. i, but in some other cases one of them was 
evidently smaller and much flatter than the other. In these cases the 
angle which the two ribs made at the summit and base was always i8o°, so 
that the two ribs formed one straight line, as in Fig. i ; but in a third form 
* % 3 4 
§ $ 7 3 s 
io ii m ia 
Thirteen kinds of seeds of Ginkgo , from which the fleshy coat had been removed ; all seen from 
the top; natural size. Fig. i. Two-angled seed. Figs. 2-9. Three-angled seeds. Figs. 10-13. 
Four-angled'seeds. 
this angle was smaller, varying for instance in three cases between 135 0 
and 160 0 . 
There was also a large number of three-angled seeds, even more than 
half the total number, but the regular form, as that of our Fig. 9, corre¬ 
sponding also to the figure given by Sprecher, was not so very frequent, as 
only one-fifth of them all had this shape. The remaining four-fifths were 
less regular and showed many transitions between the regular two-ribbed 
and the regular three-ribbed forms. The characteristic shapes were care¬ 
fully selected and photographed together; they are shown in Figs. 2-8 
at their actual size. Their difference is caused by the inequality in size of 
the three faces, two remaining nearly always equal, the third diminishing 
gradually in size; by comparing the Figs. 8 and 2, this diminution of the 
third side is clearly to be seen on the left side of each figure. In Fig. 2 it 
is so small that this seed approximates to an irregular two-angled one, the 
