CUTICLES OF CYCADEAN EEOXDS. 



157 



IT. CUTICLES OF SOME RECENT CYCADS. 



(a.) Material and Methods.— Most of the material used in tlie investigation of 

 recent cuticles was specially obtained from tlie Glasnevin Botanical Gardens, Dublin, 

 and from Kew, and was fixed in medium chromacetic acid. In some cases ordinary 

 laboratory material was used. 



The types examined included Ci/cas (5 species), JDioon (2), Ceratozamia (3), Macro- 

 zamia (6), Zamia (8), Sncephalartos (8), Bowenia (1 form), Stangeria (2 forms), 

 Microeycas being the only genus unrepresented. 



The upper and lower cuticles of the leaves were examined in surface view and in 

 section. In many cases the epidermises were stripped off easily, but in others it was 

 necessary to use Schulze's macerating fluid. Sometimes pinnae were treated with the 

 fluid and then washed in ammonia, as in the case of the fossil cuticles {vide infra) ; after 

 this treatment only the cutin layer remains, with little or no trace of underlying cells. 



Permanent preparations of cuticles removed in either of the above ways wore 

 made. Bismarck brown, Congo red, and diamant fuchsin were used for staining. 

 Lloyd (1908), in his researches on the Physiology of Stomata, seems to consider 

 Congo red more satisfactory as an epidermal stain than Bismarck brown; in the 

 present case diamant fuchsin was most used, as it is very rapid. The stain fades a 

 little, however, on exposure of the preparations. Unstained preparations of cuticles 

 were also largely used. In the case of the sections, one of the most satisfactory stains 

 was found to be Scharlach U (also used for macerated cuticles) prepared as directed by 

 Hill (1912). By it the cutin layer and cuticularised parts were clearly defined, staining 

 a bright brownish red, all the other tissues remaining unaffected. Phloroglucin with 

 hydrochloric acid was used to show the lignified lamellae which occur in every case on the 

 dorsal and ventral walls of the guard-cells. Serial sections stained with cotton red and 

 aniline blue, and with diamant fuchsin were employed in the correlation of surface views 

 and sections of stomata. Other tests were used, but an account of them need not be 

 repeated here, as descriptions are to be found in the literature quoted. 



(b.) Previous References. — The most important previous accounts of the epidermises 

 of Cycads include that given by Bornemann (1856), whose description is in connection 

 with some fossil types and includes remarks on the chemistry of the epidermal walls 

 and on the preparation of "artificial cuticles"; Kraus (1866) and Nestler (1895) also 

 give good descriptions of some Cycadean cuticles. These researches show that each 

 genus is fairly well characterised by a peculiar epidermis ; sometimes the genera may 

 be divided into sub-groups according to the structure of the epidermis (see Bornemann, 

 1856, p. 42, and Kraus, 1866, p. 13). Figures and descriptions of the stomata of some 

 Cycads are given by Schwendener (1881), Strasburger (1866-67), Mahlert (1885), and 

 Porsch (1905). More detailed references will be given in the description of each genus. 

 The last-named author mentions the fact that though there is a general type of stoma 



of the Gymnosperms as a whole, there is one special type for almost each 



o 



hen the finer structure is taken into consideration 



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