MICROSCOPIC STRUCTURE OF WEED SEEDS 



557 



Prostrate Spurge (Euphorbia* maculata L.). 



The walls of the outer cells are dark in color; these cells are 

 but slightly mucilaginous. The granular layer is not pronounced. 

 The palisade-like cells resemble those of the other species. 



Fig. 425. Microscopic structure of the seeds of the Spurge family (Euphor- 



biaceae). 

 I. Cypress Spurge (.Euphorbia cyparissias). II. Flowering Spurge (Euphor- 

 bia corollata). 

 ep=epidermis, in figure II cell-walls mucilaginous. pal=palisade cells. p= 



parenchyma cells. 

 (Drawing by L. H. Pammel.) 



Yellow Spurge (Euphorbia cyparissias L.). 



The seed shows the usual palisade-like cells with the overlying 

 and underlying thin-walled parenchyma cells. 



MALVACEAE, MALLOW FAMILY. 



Velvet Weed, Butterprint (Abutilon theophrasti Medic.).* 



The outer layer a, of the first integument is transformed into a 

 strongly refractive layer. The second layer is composed of radially 

 elongated cells. The seed hairs arise from a single cell and are 

 large and conspicuous. The hairs are spindle-shaped and thin- 

 walled; they occur mostly at the ends of the seed and are more or 

 less pressed to it. There is little or no coloring matter in this in- 



♦From Rolfs, P. H., Bot. Gaz. 1892 :33-39. 



