XXVIIl] SEEDS 27 



flesh as far as the micropyle. In other seeds the tracheal supply 

 of the outer flesh consists of several bundles and not two as in 

 Cycas. The inner flesh abuts on the nucellus and is connected 

 with it except at the apex (fig. 396, B). In ripe seeds the nucellus 

 is reduced to a thin membrane enclosing the large megaspore at 

 the upper end of which is a depression (fig. 396, B') or sometimes 

 two depressions (fig. 396, I) in the prothallus containing the 

 archegonia. In the seed of Dioon edule 1 (fig. 396, A) the position 

 of the absciss-layer (s) is indicated by a slight transverse con- 

 striction. In the seeds of Bowenia, constructed on the same 

 plan, the inner series of vascular strands appears to be nucellar 

 in position, thus differing from the strands in Dioon, Cycas, and 

 other genera which are confined to the integument. Miss Kershaw 2 

 in describing Bowenia speaks of an upper and a lower pollen- 

 chamber ; the former serves as a storage-place for the microspores 



1 Chamberlain (06). 2 Kershaw (12). 



FIG. 396. A. Seed of Dioon edule in longitudinal section; a, integument; 

 v, vascular tissue ; m, prothallus; n, nucellus; p, pollen-chamber; 

 s, absciss -layer; ar, archegonia. (After Chamberlain.) 



B, B'. Seed of Cycas circinalis; a, v, integument (sarcotesta) and 



vascular tissue; b, sclerotesta; c, inner sarcotesta; m, n, pro- 

 thallus and nucellus. (After Stopes.) 



B'. Apex of nucellus ; p, pollen-chamber ; i, integument ; n, nucellus ; 

 ch, archegonial chamber; ar, archegonia. 



C, D. Seed of Encephalartos Altensteinii; C, surface of stone. (After 



Stopes.) 



E. Stem of Bowenia serrulata; g, level of ground. (After Chamber- 



lain. ) 



F. F'. Pinnae of Macrozamia heteromera. 



G. Pollen-tube of Microcycas Calocoma. (After Caldwell.) 



H. Transverse section of stem of Encephalartos horridus; s, stele; 



g, girdle-bundles. (After Mettenius.) 

 I. Apical view of prothallus of Cycas showing two archegonial chambers 



(ch). (After Treub.) 

 K. Encephalartos Barteri. Transverse section of stem ; x, xylem ; 



p, phloem. (After Matte.) 

 L. Cycas siamensis. Transverse section of vascular tissue of young 



stem. (After Matte.) 



M. Cycas revoluta; two motile sperms. (After Miyake.) 

 N. Long hair with short basal cell from the petiole of Macrozamia 



heteromera. (After Robertson.) 

 0. Vascular bundle of Dioon edule from base of petiole; p, phloem; 



c, cambium. (After Mettenius.) 



