260 
À second criterion as to the presence of units in 
the integument is the ribbing. In the ripe seed ribs 
are to be seen, very faint on the outer flesh, but clearly 
Fig. 5. Ginkgo biloba; transverse sections through a young ovule. 
1. Micropylar region, sarcotesta with mucilage cavities, place where 
the sclerotesta begins to differentiate is dotted, the micropyle is seen as 
a triangular fissure. 2. Portion of 1, around the micropyle magnified. 
3, 4, 5 and 6 transverse sections through lower parts, the angles 
gradually dy ont. 
marked on the sclerotesta, their number being two, three 
or four. In very young ovules no trace of them is to 
