594 
Affour tit and La Riviere . 
use as morphological distinctions, our attitude towards them as criteria 
of taxonomic importance may require readjustment.’ 
The differences in number of ribs on the integument and sclerotesta,, 
respectively, of seeds of one and the same species are also recorded in 
phytopalaeontological literature regarding the seeds of Physostoma and 
of Trigonocarpus. 
As to Physostoma elegans , Oliver mentions (8, p. 83) that in the fifty or 
so specimens that came under observation the number of ribs varied from 
nine to twelve. 
There is no mention made of the occurrence of transitional forms 
between them, like those we describe for our Ginkgo and which were 
so frequent, so that our case may perhaps differ in kind from that of 
Physostoma. 
Salisbury speaks about the seeds of Trigonocarpus (10, p. 68) relatively 
to the accessory ribs occurring sometimes on the separate valves, and 
mostly under vascular bundles of the sarcotesta. Since in Ginkgo , however, 
no valves occur—the stony coat lacking fissures at the place of the ribs— 
and as vascular bundles are absent from the sarcotesta, those seeds cannot, 
as it seems to us, be compared with the seeds here described. 
In the Botanic Garden at Leyden, several Ginkgo trees are in cultiva¬ 
tion ; one of them, the largest and a very beautiful tree, may be a male one, 
although it has never been known to flower. Another one, much smaller 
and of regular conical form, produced seeds regularly during recent years, 
but probably they were not fertilized, as we never succeeded in making them 
germinate. They were also smaller and had a less developed stony coat 
than the seeds described here; these latter were probably fertilized, as it is 
reported that in former years young seedlings have been found under 
the tree at Slikkerveer. 
Summary. 
The stony coats of the seeds of Ginkgo examined, gathered from 
a single tree, showed two, three, or four ribs, and they offered at the same 
time many gradual transitions between the different forms. 
Botanical Laboratory, 
University, Leyden. 
March , 1915. 
