570 Gibbs . — On the Development of the 
Fig. 43. Tracheides as seen in the central cylinder of small-celled tissue of sterile prothallus. 
x 625. 
Fig. 44. P. bracteata . Mature strobilus, with swollen bract bases, deep purple in colour 
(Buitenzorg). Nat. size. 
Fig. 45. Longitudinal section of embryo, showing cotyledons, with plerome cylinder and cortical 
resin canals, x 8, red. |. 
Fig. 46. Longitudinal section through prothallus, showing embryo with extruding root-cap ; 
in the embryo resin canals occur both in the cortex and the pith ; procambium strands of spiral 
vessels mark the plerome cylinder; the cotyledons show similar development, each being served 
with two vascular strands, x 8, red. 
Fig. 47. Embryo dissected out. x 8, red. j. 
Fig. 48. P. neriifolia. Strobilus in earliest stage available, with four bracts, one of which is 
fertile ; the lowest pair of unmodified bracts have been cut off, showing two pairs of upper bracts, 
apparently opposite and decussate (Fiji), x 8, red. |. 
Fig. 49. Later stage, strobilus with three bracts, one of which is fertile, showing approach to 
spiral arrangement, x 8, red. |. 
Fig. 50. Strobilus of three bracts, of which two are fertile ; the caducous lower bracts have 
already been shed ; the upper ones show shrunken laminae and swollen bases, x 8, red. f . 
Fig. 51. Fertilization stage. Nat. size. 
Fig. 52. P . saligna , showing a strobilus of three bracts, of which one is fertile; the peduncle, 
in this species, is very elongated, x 8, red. |. 
Fig. 53. Basal portion of a strobilus with four bracts, showing a modification of the decussate 
arrangement, x 8, red. 
Fig. 54. P. Totara. Strobilus of three bracts, still undifferentiated, one of which is fertile; ovule 
in pollination stage, x 8. 
Fig. 55. Strobilus of four bracts, two of which are fertile; the oldest ovule shows nuclear division 
in macrospore, x 8. 
Fig. 56. Strobilus with three bracts, of which two are fertile ; the oldest ovule shows free cell 
formation in the prothallus. x 8. 
Fig. 57. Longitudinal section of Fig. 55, showing well-differentiated tapetum and enlarging 
macrospore, x 16, red. 
Fig. 58. Longitudinal section of a strobilus with three bracts ; in the largest ovule the female 
gametophyte shows free nuclear division, while the youngest is in the enlarging megaspore stage, 
x 16, red. |. 
Fig. 59. Strobilus with four bracts, of which two are fertile ; the laminae are barely indicated, 
but the bases have swollen to a large size, and are of a bright red colour ; the ovules are in the pre- 
fertilization stage, the peripheral half of the integument showing lignification of the cells. 
Fig. 60. P. Hallii. Strobilus with bases of bracts swollen and red in colour, one bract being 
fertile ; the ovule is in young embryo stage, x 8, red. |. 
Fig. 61. Strobilus in which the bract bases have remained unmodified ; one bract is fertile, 
with ovule in young embryo stage, x 8, red. |. 
Fig. 62. Longitudinal section of a strobilus with three unmodified bracts, the upper one fertile ; 
the ovuliferous scale shows stone-cell thickening in the mesophyll and very large resin canals, also 
phloem strand penetrating the integument ; the integument is entirely lignified, with the exception 
of a few cell layers in proximity to the nucellus, which is mostly digested by the prothallus; 
the latter is surrounded by a well-developed megaspore membrane and contains a young embryo, 
x 16, red. f. 
Fig. 63. Strobilus with two fertile bracts. Nat. size. 
PLATE LII. 
Fig. 64. Strobilus with bract bases unmodified and shorter than the ovule. 
Fig. 65. P. nivalis, showing a strobilus with three bracts, still undifferentiated, one of the 
lower bracts being fertile; the strobilus is in the axil of a foliage leaf of the axis, x 8. 
Fig. 66. Strobilus with two undifferentiated bracts, one of which is fertile ; the ovule is in the 
pollination stage, x 8. 
Fig. 67. Strobilus with two bracts, one of which is fertile ; enlarging macrospore stage, x 8. 
