372 XXVII. REPRODUCTION OF GYMNOSPERMS. 



ovule is in a most rudimentary condition, and is not easy to find ; 

 longitudinal sections through the ovule shows the nucellus as a 

 small protuberance surrounded by the simple integument. After 

 this a further development of the ovule takes place, and at a rate 

 which depends upon the greater or less time which has to separate 

 the periods of pollination and of fertilisation. In Taxus (the 

 Yew) fertilisation takes place about the middle of June in the 

 same year ; in the Scotch Fir not until the next year, more than 

 thirteen months after pollination, and in this case the further 

 development of the ovular rudiment begins in the spring follow- 

 ing pollination, and must therefore be studied in one year old 

 cones. In the Spruce Fir (Abies, Picea), pollination and fertilisa- 

 tion are separated by about six weeks only, and the further 

 development of the ovular rudiment follows close upon pollination. 

 We will consequently, in what follows, keep to the Spruce Fir, 

 because this offers many advantages for study. It would lead us 

 too far to follow step by step in our present studies the enlarge- 

 ment of the embryo-sac, the origin of the tissue of the prothallus 

 (endosperm) and of the sexual organs in its interior, the increase 

 in size and corresponding differentiation of the entire rudimentary 

 seed. We will therefore turn at once to the stage in which the 

 OOSpheres are fully formed, and in a receptive condition. This 

 condition, in the common Bed Fir (Picea vulgaris, Lk.), 1 is 

 reached about the middle of June, and fertilisation is then com- 

 pleted in the course of a few days. Alcohol material in suitable 

 stages of development must be at command. It is recommended 

 not to lay entire cones, but separate fruit-scales, in the alcohol. 

 Before cutting the alcohol material, it should be transferred, as we 

 have already repeatedly done, to a mixture of equal parts alcohol 

 and glycerine for at least twenty-four hours. 



In beginning the investigation, we first study the appearance 

 of the entire scale. This is obovate, shows below, on its inner 

 (upper) surface, the two ovules, and also the outlines of the mem- 

 branous wings, which later on will be separated, with the ripe 

 seed, from the inner surface of the fruit-scale. On the outer sur- 

 face of the fruit-scale, and below, can still be found the bract, now 

 appearing comparatively minute. 



The ovule to be cut can be easily separated uninjured from the 



1 Picea vulgaris, Link (1827), of the text, was renamed by the same author 

 (1841) Picea excelsa. It is Pinus Picea and Abies Picea of various authors. 



