/ 



314 MORPHOLOGY. 



group, that the sperm cells are well-fomied spennatozoids. Tn zamia each 



one is shaped somewhat like the half of a biconvex lens, and around the con- 



^^ "".T^L J- vex surface are several coils of cilia. After the 



."■.I. .'fMJs,'' pollen tube has grown down through the nucel- 



^' ;,^ ' '^A lus, and has reached a depression at the end of 



■"■ '■-■jj the prothallium (endosperm) where the arche- 



t*.*TV-._ '^i.- gonia are formed, the spermatozoiils are set 



■1 •J.-iii^^- '.^r: free from the pollen tube, swim around in a 



\'^r^,-\\i\^' '' liquid in this depression, and later fuse with 



■' ' .;\ ■ ^**4'';i'' the egg. In gingko and cycas these spcrmato- 



,' '.'. '"' '-'! j".' zoids were first discovered b}' Tkeno and Hirase 



'* ~ '.' ';"'.', in Japan, and later in zamia by \\'ebber in this 



country. In figs. 371-374 the details of the 

 male pmthallia and of fertilization are shown. 

 634. The sporophyte in the gymnosperms. — 

 ^. ■ ' '■•'" In the pollen grains of the gymnosperms we 



'""■" easily recognize the characters belonging to the 



„ ... . ' "^'. snores in the ferns and their allies, as well as in 



rertihzation m c\'cas, ^ 



small spermatozoid fusing the li\"er\vorts and mosses. They belong to the 



with the larger female nu- . . i. .1, 



cleus of the egg. The egg same series of organs, are borne on trie same 



protoplasm fills the archego- pi^^se or generation of the plant, and arc practi- 

 nium. (irom drawings by 1 " f^ ^ 1 



Hirase and Ikena.) cally formed in the same geneial w.ay, the 



variations between the different groups not being greater than those within 

 a single group. These spores we have recognized as being the product of 

 the sporophyte. We are able then to identify the sporophyte as that phase 

 or generation of the plant formed from the fer- 

 tilized egg and bearing ultimately the spores. 

 We see from this that the sporophyte in the 

 gymnosperms is the prominent [lart of the 

 plant, just as we found it to be in the ferns. 

 The [line tree, then, as well as the gingko, cvcas, 



yew, hemlock-spruce, black spruce, the giant ^,,^r^^:^ drSTt^. 

 redwooil of California, etc., are sporophytes. a tail. 



While the s]inrangia (anther sacs) of the male 

 lloMcrs o]ien and permit the spores (pollen) to be scattered, the sporangia of 

 the female flowers of the gymnosperms rarely ojien. The mac rospore is <le- 

 veloped within sporangium (nucclkis) to form tlie female jirothaliiuni (cn- 

 dosjierm 1. 



635. The gametophyte has become dependent on the sporophyte. — In this 

 respi-ct the g\ mnospcrms dilTc]' \\idrl\- from I lie jileridoplixtes, (liough we see 

 suggestions of this londition of tkings in Isnelisand Sehigindia, where the fe- 

 male prothallium is de\'(Ioped witlu'n the maeii -s] lore, and e\en in Seklginella 

 begins, and nearly completes, its developmeni while still in tlie sporangium. 



