558 TRANS. ST. LOUIS ACAD. SCIENCE. 



E. commulata : the seeds are beautifully sculptured, and ash- 

 colored {ste plate xii., fig. 19). A cross-section of the seed is 

 shown on plate xiii., fig. 6. The outer layer is made up of mu- 

 cilaginous cells, with greatly thickened colorless walls. Underly- 

 ing this layer is the granular portion, the cells of which come out 

 much clearer than in most of the species. Iodine colors the gra- 

 nules blue. Iodine causes no change in the cell-walls of the mu- 

 cilaginous layer, but with sulphuric acid it colors them blue. 

 The palisade-like cells are of the usual kind, as are also the cells 

 which follow them. 



jE. Lathyris (see plate xii., fig. 19a). This species has been 

 studied by Harz.^^ My studies do not quite agree with his. The 

 outer cells are thicker walled (see figure 9, PI. xiii.) ; the pores 

 of the palisade-cells are more numerous than shown in his sketch. 

 It appears from his investigation that these cells contain large 

 quantities of lime and silica. 



Conclusions. — From a systematic point of view the seed-coats 

 offer few characters which are of sufficient importance to use in 

 distinguishing species ; closely related species show a similar 

 structure in the seed-coats. Where the outer surface of the seed 

 shows sculpturing or marking, the minute structure shows cor- 

 responding differences, as in E. hexagona and E . marginata. 

 The ashy part, which covers many seeds, is changed into muci- 

 lage on the addition of water, and in the case of E. folygonifo- 

 lia spirals are developed. Michrochemically this substance ap- 

 jDears to be similar to the mucilage oi Limim^ Riiellia., Ocimum.^ 

 Salvia, &c. The mucilaginous part is very brittle when dry, 

 and hence in many seeds this has broken away. Underlying the 

 mucilaginous layer is a narrow zone in which starch-grains are 

 abundant. This layer occurs only, so far as I have been able to 

 make out, in connection with the mucilaginous layer. It is most 

 highly developed where the mucilaginous layer is best devel- 

 oped. Thus it appears as though it were intimately connected 

 with the formation of this portion of the seed. 



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