394 



BOTANY. 



He. 281.— 4, a male flower of A1dei> pectinit- 

 ta : 0, bracts ; a, stamens. B. pollen grain ; ^, 

 extine, with its large vesicular proiriisions, 

 bl ; i, intine ; y, cell in the interior of the pol- 



diameter centrifugally, and the sheathing envelope of bark 

 centripetally, by the growth of new tissues between these 



two portions. 



Gymnosperms are all ter- 

 restrial, chlorophyll-bear- 

 ing plants ; none are 

 aqnatic, and none are par- 

 asitic. Most of them are 

 large trees, a few only 

 being shrubs or under- 

 shrubs. 



506. — The flowers of 

 Gymnosijerms are much 

 simpler than those of the 

 . remaining Phanerogams. 

 They are always diclinous 

 — i.e., the male and fe- 

 male organs are in diifer- 



len grain developing the pollen tube: g, basal i fl„Tj,p,,o TTiPv fnnsisjt 

 ceU attaching j( to the wafi of the grain, x 300 ent DOWClS. J.ney COnslSC 



-Rafter Sachs; B after schacht. essentially of ouo or more 



variously shaped pollen-producing organs (stamens) on the 

 one hand, and naked ovules on the other ; both kinds of or- 

 gans are in most cases in structural connection with scale- 

 like'bodies, which serve as acces- 

 sory organs of reproduction. 



507. — The male flower in 

 Abies pectinata consists of an 

 elongated axis, upon which are 

 borne a large number of spirally 

 arranged stamens (a, Fig. 281, 

 A). Each stamen is morpholog- 

 ically a phyllome, which is here 

 modified into a body consisting 

 of a short stalk {filament) sup- 

 porting two pollen sacs (the an- 

 ther). The pollen grains are developed from mother-cells, 

 each of the latter giving rise to four grains. The pollen- 

 mother-cells themselves arise from the interior parenchyma 

 of tlie stamen by the differentiation and enlargement of cer- 



Fig. 282.— A catkin or spike of the 

 male flowers of Pinua .^ylvestris. — 

 From Le Maout and Decaisne. 



