388 YOUNGKEN— ON THE MYRICACEAE 



layers and an inner smaller and more round celled tissue of more numer- 

 ous layers. Prolonged into the former from the point of attachment 

 of the fruit with the axis is a vascular tissue that on entering the outer 

 layer ramifies abundantly and as above stated gives off delicate diverti- 

 cula to the different emergences. At this time only slight indication is 

 observed of a difference in cell contents between the outer and the inner 

 zone. The endocarp is a shallow and delicate layer that from now on 

 becomes less and less conspicuous. By mid June or soon thereafter 

 striking changes begin to appear. The epidermis, as well as the meso- 

 phyll cells of the emergences, the general epidermal (epicarp) cells of 

 the fruit wall and the outer zone of the mesocarp have all enlarged 

 steadily and become filled with an abundant secretion which assumes a 

 bizarre coloration when stained with Safranin and Methyl Green. Tints 

 varying from neutral-gray through pink, crimson, crimson-green, green- 

 blue, yellow and brown are all present in distinct but neighboring cells 

 and though the writer has as yet been unable to apply abundant tests, 

 the above coloration suggests the formation and presence already of 

 the palmitic, myristic and stearic acids already tested for and recorded 

 by pharmacists and synopsized by Chevaher (7, p. 159). 



At this time the inner layer of the mesocarp contracts conspicuously 

 with the last, its cells remaining small, thin walled, rounded and its 

 cavities filled with delicate protoplasm. 



A further stage in the maturation of the fruits is noted by the middle 

 or latter part of July. Each knob-shaped emergence has developed 

 around itself an abundant waxy layer which, by hardening, gives a 

 bluish white color to the fruit surface. The mesophyll cells of these hairs, 

 as well as 3 to 6 of the innermost cell layers of the outer zone, become 

 loaded with cell contents that assume a uniform red or reddish-green 

 hue which even heightens the bizarre coloration noted above. By this 

 time also the cells of the inner zone have become largely thickened from 

 within-outward by lignified thickening and the cells themselves, having 

 increased greatly in size and become markedly sinuous in outline, assume 

 a bright red staining with Safranin. 



The thickening process clearly proceeds in centrifugal fashion for 

 in mid or late July the inner walls, surrounding the ovarian cavity, 

 may be highly lignified and stained a bright red hue, while as yet the 

 external cells adjacent to the outer zone are little, if at all, altered in 

 shape or lignified. Progressive lignification of this area gives rise by 

 mid August to the extremely hard scleroid fruit layers that efficiently 

 protect the enclosed seed. 



