Bamaley: anatomy of onagraceae. 689 



Conclusions. 



There seem to be no marked anatomical characters of the 

 stem which can be set down as belonging to one species and to 

 no other. Plants of the same species growing under different 

 conditions may present as great differences as are to be noted 

 between species of comparatively remote genera. Slight diff- 

 erences in the thickness of the various zones of tissue are evi- 

 dent, as are also variations in the size of the constituent ele- 

 ments in some of the tissues. The following generalizations 

 may be drawn. 



1. There is a striking similarity in stem structure througout 

 all the seven genera examined. The stem anatomy will not 

 serve to distinguish one genus from another. 



2. The cortex is absent from old stems, being replaced by 

 cork of characteristic structure. 



3. The normal phloem is in all cases poorly developed. 



4. Bicollateral vascular bundles occur in all the species ex- 

 amined. 



5. Intra xylar phloem islands are found in the stems of all 

 the robust species. 



6. Raphides of calcium oxalate are present in all cases. 

 These generally occur in both cortex and pith, often in the per- 

 icycle and phloem. 



EXPLANATION OF PLATES. 

 Plate XXXVI. 



Anogra pallida. — 1. A crystallogenous cell in the pericyele seen in longi 

 tudinal section. 2. Transverse section of a portion of an old stem; show- 

 ing bast, inner pericyele and cork; two crystallogenous cells in the peri- 

 cycle. 3. Longitudinal section showing cork and adjacent cells. Kaphides 

 of calcium oxalate are shown in one of these. 4. Surface view of cork. 



Oalpinsia hartwegii. — 5. Cork in longitudinal section, showing sclerotic 

 cells. 6. Cork and subjacent tissues. 7. Cork in transverse section. 8. 

 Portion of a tangential longitudinal section through the secondary wood; 

 medullary rays cut across. 9. Portion of the epidermis, surface view. The 

 two kinds of hairs are shown. 



Kneiffia fruticosa,. — 10. Pith and primary wood; medullary phloem groups 

 composed of small thin walled cells. 11. A trichome. 12. Young epider- 

 mis. 13. Stereome cells. 14. Epidermis of older part. 



Kneiffia glauca. — 15. Crystal sac in the pith. 



Kneiffia pumila. — 16. Transverse section extending from secondary 

 xylem to cortex. 



Megapterium missouriensis.—n . Transverse section of the extni-xylar 

 portion. 



