6 CYCADALBS [CH. 



lateral strobiH has recently been described by Chamberlain ^ who 

 figures a stem of Macrozamia Moorei with fertile shoots wedged 

 among the persistent petiole-bases, a condition very similar to 

 that in the Mesozoic Bennettitales. Pearson has also described 

 clear cases of laterally-borne cones in Encephalartos. Cycas 

 exhibits two kinds of branching, the female plants being mono- 

 podial while in the male the branching is sympodial. The micro- 

 spores are produced in sporangia grouped in more or less well 

 defined sori (figs. 389, A; 392, E— G). There is no definite 

 annulus, but in the occurrence of groups of thick-walled cells 

 some microsporangia recall those of certain ferns^. The ovules 

 vary considerably in size, sometimes exceeding 5 cm. in diameter : 

 there are usually two on each megasporophyll (figs. 393, C; 

 394; 395, Id) but in most species of Cycas (fig. 392, B) and 

 occasionally in other genera the number is larger^. A thick 

 integument encloses the nucellus with which it is fused except 

 in the apical region (fig. 396, A, B). Below the comparatively 

 long micropylar tube is a well-developed pollen- chamber (fig. 396, 

 B', p), a striking feature of Cycadean ovules, immediately above 

 the megaspore; the latter is filled with prothaUus-tissue and 

 bears a small apical groiip of archegonia on the floor of a depression 

 (fig. 396, A — B'). In Microcycas^ as many as 200 archegonia 

 are recorded — a very exceptional case — and these are not confined 

 to the apical region, though only the apical archegonia are 

 functional. Each archegonium is characterised by a very large 

 oval egg-cell and a much reduced neck^- The microspores usually 

 produce a single prothallus-cell, a stalk-cell, and body-cell, and 

 from the body-cell are developed two spirally ciKated spermato- 

 zoids (fig. 396, M). In this respect also the monotypic genus 

 Microcycas is pecuhar : it may have as many as 8 body-cells 

 and 16 male gametes in a single pollen-tube (fig. 396, G), while 

 in Ceratozamia^ 4 gametes have been seen in one tube. The 

 poUen-tube grows like a fungal mycehum into the nucellar tissue 

 and the male gametes are formed in the distended proximal end 



1 Chamberlain (13). ^ Lang (97); (00). 



' Chamberlain (09) p. 410. * Caldwell (07). 



5 For fignrea and references, see Coulter and Chamberlain (10). 

 « Chamberlain (12) p. 11. 



