300 
the units. Traces of them are principally pointed out by 
the main-ribs, and as in Trigonocarpus by three small 
sutures at the micropyle. The testa is composed of the 
three characteristic layers, which appear in nearly all 
Gymnospermous seeds and are here already present in the 
most differentiated condition. 
Externally a very striking difference between Trigono- 
carpus and Mitrospermum is the round shape of the former 
in transverse sections, contrary to the flat shape of the 
latter seed. Both types the threemeric and the twomeric 
occur among the gymnospermous seeds. 
Though the number of integumental units is not a con- 
stant one, and there is always a good deal of fluctuation 
in it, it varies around a middle-worth, characteristic for 
each genus. It is suggested by Oliver (104 p. 102) that 
a great number of units or slips represents a more primi- 
tive stage, and he composes a series of them, in which 
Physostoma with about ten tentacles stands highest then 
coming Lagenostoma with nine, Sphaerostoma with eight 
a. s. o. Amongst the Trigonocarpeae this variability 
seems to be less fluctuant according to Salisbury 
(126-5270); 
These series show us that there is a gradual transition 
between a primitive stage of the testa in which it is com- 
posed of a great number of units to that one of their 
entirely fusion with only slight indications of their mul- 
tiple origin. 
The ovules are always borne on leaves, slightly different 
from the ordinary trophophylls and bearing resemblance to 
the fertile fernleaves. Strobili are not formed. 
The value we may attribute to the cupule of Lage- 
nostoma and Sphaerostoma is of great importance. And 
though this is still uncertain, it may be quite possible for 
the present, that those cupules are formed by the pinnae 
of the sporophyll bent around the integument. When in 
