272 BOTANICAL GAZETTE [. tfm 



walled cells elongated either tangentially and arranged end to end in 

 longitudinal rows, or radially forming a palisade layer. The walls 

 are sinuous with numerous pits, and after maceration the margins of 

 the outer and inner tangential walls are seen- to be lobed, each lobe 

 branching with the ends overlapping and fitting together to form a 

 flat compact layer (fig. 18). The empty cell cavities are compara- 

 tively small and present a striking oval appearance in median 

 section. 



4. Parenchyma. — Many cell layers of spongy parenchyma, dif- 

 fering greatly in size and shape, make up this layer. The cells of the 

 outer layers are usually small and frequently sclerenchymatized and 

 pitted. Within these small cells are one or more layers of either large 

 or small stellate cells having very large intercellular spaces. Their 

 thin walls are usually sclerenchymatized and often pitted or reticu- 

 lated (Cucurbita). The remaining layers consist of small, thin 

 walled spongy parenchyma cells containing chlorophyll in some 



species. 



mbedded in this parenchyma 



usu 



on the flattened surface of the seed. 



pidermis.~A single layer of small, polygonal, and incon 



forms 



Perisperm.— This thin coat is collapsed 



of small. 



very 



lied 



nent with Javelle water brings to view several layers ot snwu. 

 thin-walled cells covered with an epidermis having cuticulanzed 

 outer and radial walls. No contents are evident. 



Endosperm.— This consists of one layer of very thick-wa 

 polygonal cells, containing oil and protein granules. A few excep- 

 tions (as Citrullus vulgaris) have within this layer several m 

 of empty thin-walled cells. „ 



EMBRYO.-The leaf-like cotyledons have an epidermis of sma 

 cells below which, on the inner side, are two sharply defined pab* 

 layers. Procambium bundles run through the small-celled mesoptt) 



laver- 



All 



globoids and crystalloids which are very 

 no diagnostic importance. 



minute 



attaining 

 ill)' 



