

KEY TO SPECIES OF NUTS. 37 



II. Epidermis of periderm containing no stomata Continued. 



A. Epidermis of periderm with stone cells Continued. 



2. Stone cells well developed. 



a. Stone cells, single or in groups, usually forming noticeable 

 papillae; inner and lateral walls marked with variously- 

 formed pores; rosette crystals often present, 

 a Stone cells forming distinct rounded papillae, especially along 

 the vascular bundles, their size not affected by location; 

 endodermis indistinct; aleurone layer mostly single. 



Amygdalus communis (hard-shelled), p. 10. 

 /3 Stone cells often forming flat-topped papillae; groups of 

 small stone cells along vascular bundles; endodermis com- 

 paratively distinct ; aleurone tissue of four or more layers 



of cells Amygdalus persica, p. 13. 



Z>. Stone cells evenly distributed, their size not affected by loca- 

 tion, dome-shaped ; pores mostly circular ; epidermal cells 

 polygonal; rosette crystals absent. 



a Stone cells mostly under 100 /* long ; intercellular spaces 

 small and slightly affecting form of stone cells; endo- 

 sperm of single layer of cells Prunus armeniaca, p. 12. 



/3 Stone cells frequently over 100 /* long; intercellular spaces, 

 large, noticeably affecting shape of stone cells ; thick 

 masses of endosperm along the lateral faces of the 

 kernel Prunus domestica, p. 14. 



B. Epidermis of periderm without stone cells. 



1. Epidermis of periderm of angular, thick-walled cells. 



a. Middle periderm layer of branched cells; endodermis of cup- 

 shaped cells with tracheidlike thickenings in the walls. 



Canarium indicum, p. 35. 



2. Epidermis of periderm of variously-shaped cells usually with inter- 



cellular spaces. 



a. Endodermis of very small polygonal cells with thick, beaded 

 walls; endosperm and perisperm of variable thickness and 

 incompletely distributed; cotyledons green. 



Pistacia vera, p. 31. 



3. Endodermis not characteristic; outer tissues of periderm resemble 



the epidermal cells in shape; endosperm of one or two cell layers 

 continuous; cotyledons white Corylus avellana, p. 27. 



4. Epidermis of integument indefinite or absent. 



a. Integument consisting of elongated cells several hundred microns 

 in length; characteristic structures absent; aleurone grains 



very small Pinus sp., p. 28. 



&. Integument of roundish, flattened cells; embryo differentiated 

 into cortical and medullary regions ; aleurone grains large, 

 a Endosperm of about two cell layers ; rosette crystals absent 



from integument BertJwlletia nobilis, p. 29. 



/3 Endosperm of single cell layer; rosette crystals present in 



integument Lecythis usitata, p. 30. 



c. Integument of indefinite outer layer of delicate, colorless cells; 

 inner layer of brown tissue. Endosperm inconspicuous; epi- 

 dermis of cotyledons of angular cells with beaded walls; 

 kernel contains starch Anacardium occidentale, p. 33. 



