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VIII. — On the Histology of the Ephedreae, with Special Reference to the Value of 

 Histology for Systematic Purposes. By R. J. D. Graham, M.A., B.Sc, Carnegie 

 Research Scholar, Botanical Department, The University, St Andrews. Com- 

 municated by R. A. Robertson, M.A., B.Sc, F.R.S.E., F.L.S. (With Three 

 Plates.) 



(MS. received April 30, 1907. Eead June 10, 1907. Issued separately February 20, 1908.) 



Part I. — Primary Structure of Stem. 



Although a few papers have been published a number of years ago on the genus 

 Ephedra, the authors have treated the subject mainly from a systematic standpoint. 

 Thus, while the characters of the floral organs have been carefully examined and 

 described, the structure and character of the vegetative organs have only received 

 passing reference. It is proposed in the following notes to undertake the study of the 

 histology of the vegetative organs, and thereafter to ascertain how far this knowledge 

 applies to the determination of species. The following notes deal with the histology 

 of the primary stem. 



The material used, including in all 16 species and varieties, was kindly supplied 

 from the following sources : — 11 species from the Director of the Royal Botanic Garden, 

 Kew ; 8 species from the Director of the Royal Botanic Garden, Edinburgh ; 2 species 

 from Professor Trabut, Algiers ; E. Helvetica from Professor Schroeter, Zurich ; 

 E. altissima Helvetica from Professor Flahault, Montpellier, — to all of whom I here 

 tender my thanks. Material for the study of 3 species was purchased from the 

 Botanical Supply Association. For permission to examine the living specimens in the 

 Royal Botanic Gardens of Kew and of Edinburgh I have to thank the Directors of these 

 Gardens. 



(Ecology. — The genus Ephedra, consisting of some 32 species, belongs to the 

 Gnetacese, an order of the Gymnospermse. The majority of the species are found in 

 the desert parts of both the Old and New Worlds. Correlated with their physiologically 

 dry surroundings, the plants exhibit to a very marked degree various xerophilous 

 adaptations. The leaves in almost every species are reduced to mere scales, while the 

 green colour of the stem shows that the photo-synthetic functions are carried on there. 

 Further reduction of transpiration is effected through the sinking of the stomata in 

 furrows, while each stoma lies in a deep depression of the epidermis. The tender apex 

 is surrounded by many envelopes of leaves, being thus protected from excessive 

 insolation. At the approach of the dry season many species lose a great number of the 

 young branches, thereby leaving only the more mature stems to function through the 

 dangerous period of the year. The erect broom-like habit, so characteristic of many 

 species, exposes a minimum area to the strong light of the noonday sun, while the 



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