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 (i2 mm.) it perennates over the summer and succeeding winter, on a stalk 

 lo 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 uvibo 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 perennaiing 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 1^-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 apophysis-\t^\ox\ 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 ^). 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 fx, with vacuolated cytoplasm, and a large 

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

 expresses the relic of an arc/iegonium, now sunk in the tissue of the prothallus. 



A^ote. 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 ' lube-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. IMore than one grain may so germinate. 



Embryology recapitulates in minimum form the case of a coenocyiic 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. Tlie 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. 



A'ote. 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 

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

 homologous with the endosperm of the Angiospcrm. 



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 ferlilizalion (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 



