220 
Hill ’ — Studies in Seed Germination. 
however, appears to be formed on the splitting up of the petioles into 
strands, but apparently a kind of absciss layer of suberized tissue is laid 
down, along which the separation takes place. With the friction of the 
Text-fig. i. Marali horridus. Petiole oi one cotyledon from the split portion of the petiole 
tube in transverse section, showing the commencement of the further splitting into three strands, each 
of which will have a vascular bundle. The outer cortical tissues have been worn away. 
Text-fig. 2. M. horridus. Unit strand of split petiole with active pericycle. 
soil and increasing age of the seedling, the outer tissues of the petioles cease 
to function, and become somewhat disorganized and form an irregular layer 
of suberized cells. 
