CYCADACEAE 95 



generally also various bacteria present in these intercellular 

 spaces. 



It is not certain what the function of these roots 

 may be; but they probably assist in the nutrition of the 

 plant, thus functionally corresponding to the mycorhiza of 

 some conifers (Pinus, Podocarpus). 



The stems and leaves have no resin-ducts ; but the 

 former possess numerous branched slime-tubes in the inner 

 bark, hence when they are injured an ample flow of a 

 gummy fluid appears, which soon seals the wound. The 

 same result takes place when a cone or a portion of it is 

 removed, the transparent fluid gradually hardening into a 

 brittle gum. 



The stems of Stangeria are subterranean, usually con- 

 sisting of two or three stout branches, while those of most 

 species of E?icep/iaIartos are generally simple, branching 

 only occasionally and then probably owing to some injury. 

 Most species of the latter genus, however, often produce 

 young shoots from the subterranean portion of the stem, 

 thus giving rise to tufts of plants. Such shoots may be 

 planted like cuttings. The vitality of the plants is 

 astonishing. Trunks of Encephalartos Altensteinii^ which 

 had been kept lying in a shed for four years, were sent to 

 us from KafTraria and, on being planted, produced new 

 leaves the next summer. 



The leaves of Encephalartos are arranged in superposed 

 whorls, a new tuft of leaves appearing every second year 

 in alternation with whorls of flowers*. The young leaves of 

 all species when still tender are often attacked by the larva 

 of a black and yellow moth (Zeronopsis leopardina), but when 

 fully developed they are as rigid as horn, especially those 

 of E. Altensteinii and E. Eehmanni, resembling in their 

 anatomical structure the leaves of some conifers. The 

 epidermis consists of small thick-walled cells, below which 



* Plants do not flower regularly in their native habitat, there being often intervals of 

 five or more years, probably according to the nature of the season. 



