CRYPTOGAMS AND PHENOGAMS 



551 



Fig. 378. — Norway Spruce. Ovule out vertically and enlarged to show the 

 embrj'o-sac («?) filled Ijy the prothallus or endosperm and two archegonia 

 (o), each with its nock (c) and swollen iJart (o) which contains an egg- 

 cell with a nucleus («); the nueellus (nc) surrounded by the intconments 

 (i) ; pollen-grains (p) from which come pollen-tubes (() extending to the 

 archegonia; and a part of the seed-wing (5). (Strasburger.) 



Pinus and related genera will doubtless be sufficienth' clear without 

 further explanation, but the carpels and ovules call for more de- 

 tailed examination. Each carpel, as we have seen, bears two ovules 

 on its upper side near the base (Fig. 25S, 8). When cut in half 

 vertically such an ovule exhibits the parts showoi in Fig. 378. A 

 single macrospore organically connected with the surrounchng tissue 

 constitutes what is termed the emhryo-sac (e). The rest of the ovule 

 represents the macrosporangium, which is divided into a central 

 part, the nueellus ' (nc) in which the embryo-sac is embedded, and 

 an outer layer, called the inlegument (i), which covers the nueellus 

 except at the micropyle. Microspores, /. c, pollen grains, intrusted 

 to the wind, arc carried to the pistillate flowers. Caught by a 



' Nu-cel'lus < L. nucella, a little nut. 



