226 /\. P. Gregory. 
THE SEED CHARACTERS OF PISUM SATIVUM. 
rnHE fact that the seed characters “round” and “wrinkled” in 
i Peas are inherited in accordance with Mendel’s law renders 
the histological nature of the difference between the two forms 
important. Microscopic examination of the seeds reveals a 
difference in the form of the reserves stored in the cotyledons of 
the two forms, 
The starch occurs in grains of two very different and definite 
types, which can he distinguished at a glance. 
In the round seeds the peripheral cell-layers of the cotyledons 
contain dense protoplasm with a few oval starch grains which do 
not exceed 0*06 mm. in their greatest dimension. In the third layer 
of cells the starch grains reach 02 mm. in length, while the more 
deeply situate cells are crowded with large oval starch grains 
measuring as much as 0*34 mm. in their greatest dimension. The 
grains are regular in shape, with a definite centre surrounded by 
well marked lines of stratification. 
In the wrinkled peas the starch grains of the peripheral layers 
are of about the same size as those in the round peas, but are of a 
different type, occurring as irregular spheres with several centres, 
thus forming a compound grain which has a strong tendency to 
break up into smaller parts. 
In the cells which lie more deeply, these compound grains reach 
a diameter of 0*18 mm. or rarely 0*2 mm. The component grains 
never attain a greater length than 0*1 mm. in their greatest 
dimension. 
The accompanying figure will make clear the striking difference 
between the two forms of starch. 
