﻿OVULATE CONES. 



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micropylar tube, usually 5 mm. in length by 3 mm. in diameter in the radial, and 

 sometimes as the result of lateral compression only 1 mm. to 1.5 mm. in the tan- 

 gential direction to the fruit. This lateral compression, however, varies greatly in 

 extent. Sometimes one side of the seed may be markedly flattened, but the middle 

 transverse section is usually quite regularly elliptical, the long diameter being a 

 little less than twice that of the short. A characteristic peculiarity of form is that 

 the vertical longitudinal section is subrhomboidal, the seeds thus tending to arrange 

 themselves in an appression series, as shown in plate xxv, photograph 6. The 

 micropylar tube, which projects stigma-like a little beyond the pericarp of expanded 

 interseminal scales, adds to the total length of the seeds about 2 mm., or not quite 

 so much. 



Fig. 62. — Cycadeoidea lurtita. S. 113. X 30. Surface of a single seed as seen in a section tan- 

 gential to an accidentally appressed and flattened side, showing prismatic layer one cell thick covered 

 by outer husk of stringy cortical cells several cells deep at seed base and thinning out toward tip. 

 The seed husk is formed simply by the extension of the cortical region of the pedicel, the prismatic layer by the ex- 

 tension and shortening of the cells o( the endodermal or sheath region of the pedicel bundle. When shed the loose 

 seed, about the size and form of a small grain of rye. would be disengaged from the husk, the true outer integu- 

 mentary surface being formed by the more or less distinctly hexagonal cells of the prismatic layer as arranged with 

 approximate regularity, suggesting the appearance of a short ear of corn. The figure is drawn from a photograph 

 thirty times natural size. 



Exclusive of the basal outer husk the testa inclosing the nucellus is single- 

 walled and double-layered. What is here regarded as the true outer layer of the 

 seed, or outer layer of the shed seed, is made up of large, much-lignified cells, of 

 squarish outline in longitudinal section. In tangential section these cells are seen 

 to arrange themselves in rows, and are of pentagonal to hexagonal outline. They 

 are very heavily walled, the interior wall being by far the heavier. Sometimes 

 they may be seen over a considerable area where a seed is cut along a flat, more 

 than usually pronounced appression surface, as shown in figure 62. These cells are 

 not to be confused in any way with the rows of thin-walled cells of the embryo 

 ground tissue in Benncttitcs Moricrei (cf. 82, plate iv, fig. 54). The tissue of the 

 inner of the two layers of the testa is usually preserved in these sections as a 

 narrow, deeply iron-stained zone, probably of collapsed cell walls. Following these 

 two testal layers there is commonly a zone of clear quartz, bounding the nucellar 

 wall, which is usually very well outlined in all sections. The outer layer of thin- 

 walled elongate cells continues on into the micropylar tube as its innermost layer 

 or wall, and is frequently to be seen in longitudinal sections. A possible example 

 of a preserved lateral surface of the nucellar epidermis is shown on plate xxviii, pho- 

 tograph 3, and the continuation into the micropylar tube is clearly to be seen in 



