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REPRODUCTIVE STRUCTURES. 



photograph No. 2, plate xxvni. The nucellus thus fills most of the interior cavity 

 of the thin-walled seed. Inside it is a megaspore membrane. The description of 

 the seed walls as now given applies throughout their entire length, the wall of the 

 basal portion of the micropylar tube differing scarcely at all from the lateral wall of 

 the seed. Further sections from cones of various trunks are yet to be made, but 

 there is no indication in any of the fruits with a fairly complete pericarp of inter- 



Fig. 63. — (1) Bennettites Morierei Saporta et Marion. Longitudinal section of seed. From Lignier. 



a. Micropylar lube ; b. prismatic layer : c, pulpy tissue ; d, corpuscular mass ; e. interseminal scale ; t. embryo 

 space ; 8. remains of nucellus ; h. chalaza ; i, tubular envelope ; k, mycropylar canal ; I , nucellar beak : 

 m. pollen chamber ; n. fibrous stratum ; o, basal expansion of n ; p. pedicel bundle. 



(2) Cycadeoidea Wielandi Ward. Longitudinal section of seed. 12. 



a, Micropylar tube ; b. expanded summit of interseminal scale ; c. a slightly palisaded layer of heavy-walled 

 cells one cell thick, which forms the true external coat of the seed, but is covered in all the basal region of 

 the seed by the woody and tubular cells of the cup-like extension (k) of the cortex of the seed pedicels as 

 illustrated in the preceding figure 62 ; e, wall of nucellus ending below the chalaza in an expanded cup- 

 shaped base made up of short scalariform tracheitis; f, a structureless zone, or simply space between e and 

 8, in all the upper portions of the seed ; g, stringy remains of cells expanding into cup form below : h. 

 chalaza : i. woody scalariform tissue ; k, continuation of the heavy-walled tubular cells forming the outer 

 layer of the seed pedicels, which overlaps the outer layer of the seed (c) and forms a cup-like seed support 

 or husk : I , central bundle of the seed pedicel from which arise the several tissue systems of the seed walb 

 and seed interior to the outer prismatic layer ; m, remnant of aborted seed and micropylar tube at center 

 of summit of interseminal scale. 



seminal scale heads, of as complex structure of the integument as in the seeds of 

 Bennettites Morierei, although the interior layer of the micropylar tube, as in that 

 form, is regarded as a continuation of the wall of the nucellus. 



The nucellar wall is the only structure thus far certainly observed to inclose 

 the megaspore region or the embryo, as the case may be, in Bennettites Gibsoniamis 

 and Morierei. Heuce it is of importance to note that in some of the C. Wielandi 



