94 CYCADACEAE 



The fertilised ovule ripens into a drupe-like seed, 

 which in the S. A. species is bright orange, the outer layer 

 of the integument forming the skin, the middle layer the 

 pulp and the inner layer with some portion of the nucellus 



the stony shell, while the remaining tissue of the nueellus 

 forms a eopious endosperm. When the ripe seed drops 

 from the cone the embryo is very minute, completing 

 its development slowly while the seed is in the ground. 

 The pulpy eoat of the seed contains sugar and attraets 

 birds as well as small rodents, which earry the seeds about 

 and thus disperse them. 



The embryo possesses two eotyledons, and when fully 

 developed, which process may take six months or more from 

 the time that the seed was dropped, it begins to germinate. 

 The hypocotyl lengthens considerably and the radicle 

 develops into a taproot with lateral rootlets and a 

 peculiar kind of coralliform, upright roots (apo-geotropic) 

 (Figs. 62, 63), which reach to the surface of the ground. 

 In a certain circular layer of their tissue these roots 

 harbour masses of a green alga \_Nostoc punctiforme 

 (Kiitz.) Hariot]*. 



This zone of the tissue of the root consists of narrow, 

 cylindrical cells, arranged radially in such a way that 

 equally large intercellular spaces are left between them. 

 These spaces contain a slimy fluid, in which are embedded 

 innumerable threads (green) of the Nostoc, quite similar in 

 appearance to those figured on Plate 2, rig. M, 2 and 3. 

 These roots are not confined to seedling plants, but are 

 also formed by the adult plant later on. We have a good 

 sized tree of E. Altcnstei?iii in our garden, which was 

 planted some years ago as a bare trunk without any root 

 to it, and which is now surrounded at its base, close to 

 the stem, by compact masses of these roots, which are 

 peeping out of the ground here and there. There are 



* Sometimes called Nostoc Hederulae Men. and by others Anabaena Cyeadearum 

 Reinke. According to Professor N. WlLLB it does not belong to the latter genus. 



