ment-lips, the cone-scales are pressed together by subsequent growth, and the whole 

 system is inverted by a curvature of the cone-axis. In this stage, with little further 

 growth (12 mm.) it perennates over the summer and succeeding winter, on a stalk 

 10 mm. ; the scales sealed by resinous exudation, and exposed scale-facets covered 

 with a cork-layer. These facets with the pointed ' mucro ' as the first formed tip of 

 the cone-scale persist as the umbo of the adult cone. 



Note. The pollen-grains germinated on the nucellus, with short haustorial 

 germ-tube, perennate over the winter; the megaspore continues to grow as the 

 female prothallus, and is -25 mm. long in the perennating stage; the two sexual 

 plants in this condition being separated only by a few cells of the nucellar region. 



Further development takes place in the spring of the second season. By the 

 end of June (13 months after pollination) the green cone is i--2 in. long, conspicuous 

 at the end of the previous season's growth ; the cone-scale facets in spiral pattern (5 : 8), 

 closely-compacted, with green secondary extension of an afiop/iysis-region retaining the 

 central umbo of the younger stage. 



The Female Prothallus : The ovules (2 per scale), grown to 4 mm. long, are 

 protected 5 mm. below the surface by the overlap of 3 scales, so far non-sclerosed. 

 The enclosed prothallus is a cellular mass, 3 mm. long, of simple thin-walled units 

 (50 /x). Such ovules are readily cut in median longitudinal section, showing attach- 

 ment to the scale-surface along one side, integument, micropyle, nucellus-apex, pollen- 

 grains in situ, and prothallus with oospheres (3-5), 2-3 being cut in one section, at 

 the micropylar end. 



The oospheres are large oval cells, 400 /*, with vacuolated cytoplasm, and a large 

 nucleus, 100 p. Each oosphere with trace of 'neck-cells' and 'ventral canal cell' 

 expresses the relic of an archegonium, now sunk in the tissue of the prothallus. 



Note. The female prothallus is cellular, with remains of definite archegonia, but 

 is wholly enclosed and parasitic on the tissues of the nucellus : i. e. remaining inside 

 the megaspore, and within the megasporangium wall. 



Pollen-tubes digest irregular tracks through the nucellus and penetrate the 

 oospheres. Fertilization (siphonogamic) takes place about June 25. 



The Male Prothallus : Germination of the pollen-grains begins before they 

 are matured as spores : two vestigial prothallial cells are cut off, and may persist as 

 traces in the wall of the free grain, the visible nucleus being that of the third cell : 

 this delimits a ' tube-nucleus ', 'stalk-nucleus ', and a central unit, separated by cell-walls; 

 from the last, two male gamete-nuclei are produced, which pass down the pollen-tube. 

 Only one is used in fertilizing one oosphere. More than one grain may so germinate. 



Embryology recapitulates in minimum form the case of a coenocytic embryo, 

 now restricted to the base of the large oospore : more than one oosphere may be 

 similarly fertilized (Polyembryony) ; and the product of one oospore branches to 

 4 ' head '-regions, these being thrust down into the endosperm-tissue (prothallial) on 

 elongated 'suspensor' units. 



A condition generally described as 3 tiers of 4 cells each, gives 4 embryo-head 

 cells on 4 suspensors, attached to 4 rosette-cells. The head-cells segment to multi- 

 cellular constructions in which a stem-apex, cotyledonary outgrowths, and a radicle- 

 end are differentiated, without special reference to the plan of cell-segmentation. 

 Ultimately one ' embryo ' grows at the expense of all the others, with distinct radicle, 

 plumule, hypocotyledonary axis, and 3-8 cotyledons, embedded in the endosperm. 



Note. The ovules do not increase in size after fertilization ; the embryo is 

 parasitic on the cells of the female prothallus; the latter is conveniently indicated as 

 endosperm since it stores food-material in the seed-stage, although not strictly 

 homologous with the endosperm of the Angiosperm. 



Seed-stage : Food-supplies accumulate in the endosperm as starch and fat ; 

 ultimately all are converted into fat ; the peripheral layers undergo sclerosis as stone- 

 cells of the testa (mainly nucellar in origin). The cone-tissues rapidly harden by 

 general sclerosis, immediately after fertilization (hard-cone), and the whole loses water 

 as the tissues die. A slip of tissue delimited from the cone-scale surface remains 

 attached to the seed as it is also abstricted, and constitutes a 'wing '-extension. The 

 adult seed is 4 mm. long, with pointed micropylar end. A flat asymmetrical, unilateral 

 wing-lamina, 10 mm. long and broadest about half way up, subserves wind-dispersal ; 

 but the seeds possess little vitality when air-dried. 



14 



