396 



J30TANT. 



is in nearly all the class essentially like the ones described. 

 The exceptions, which are in the order Gnetaceas, will be de- 

 scribed further on. It may be pointed out here that in pass- 

 ing up through the three orders of the class, the pollen sacs, 

 which in the first resemble sporangia, become more nearly 

 like the anthers of the Monocotyledons and Dicotyledons. 



FIG. 285. 



FIG. 286. 



FIG. 287. 



Fig. 285. A, pollen groins of Biota orientalis before their escape from the pollen 

 sac ; 1., fresh ; //. and ///., after lying in water, the extine, e, having been stripped 

 off by the swelling of the inline, i ; the protoplasmic contents are seen to consist 

 of two cells, a large nucleated one, and a smaller one. B, pollen grains of Finns 

 pinaster, before their escape from the pollen sac ; , extine, with its vesicular protru- 

 sions, ol; IV., side view ; V.. dorsal view the protoplasmic contents are divided 

 similarly to those in A. Magnified. After Sachs. 



_ Fis. 286. A, a pollen grain of Cupressua sempervirens, showing the envelopes (ex- 

 tine and intine), and the rudimentary prothallium as a small cell cut off from the 

 cell contents. ]B, a germinating pollen grain ; e, the fragments of the ruptured and 

 exfoliated extine ; i, intine ; tp, the base of the pollen tube. X 400. After Schacht. 

 Fig. 287. Pollen grains of Ceratozamia lonyifolia. A, before germination ; y, 

 a three-celled body, the rudimentary prothallium. H. a (Terminating pollen grain ; e, 

 the ruptured extine ; ps, the pollen tube ; y, rudimentary prothallium. Magnified. 

 After Juranyi. 



508. The pollen grains, like the male flowers themselves, 

 are essentially alike, although differing considerably in ex- 

 ternal appearance. The vesicular protrusions of the ex- 

 tine (U, Figs. 285, B, and 281, B}, which are common in 

 certain genera of the order ConifercB, at first sight hide the 

 close similarity which exists between the pollen grains in 

 many cases. (Compare A,_I., in Fig. 285, with B, IV. of the 



