770 



PHYSIOLOGY. 



4. Lycopodiacea or Club-Mosses. — The two reproductive organs 

 of this order are termed oosporangia or oophoridia {figs. 798 

 and 801), which represent the female; find 2)ollen sporangia or 

 antheridia {figs. 799 and 800), which are regarded as male organs. 

 The contents of the pollen sporangia are called S7nall sj^orea 

 {microspores), in which sperm-cells that produce spermatozoids are 

 contained {fig. 1111, c) ; and those of the oosporangia are termed 

 large spores, macrospores, or megasporcs {fig. 801). In Lycopo- 

 dium only microspores have yet been detected. 



It is not till some months after being sown that the spores 

 commence to germinate, nor are the spermatozoids produced till 

 a nearly equal period has elapsed. In germination, the spoi'e 

 {macros2)ore) produces a very small prothallium {fig. 1112, _p), 

 on which archegonia {fig. 1113, a) are subsequently developed. 

 Each archegonium {fig. 1113, a) consists of an intercellular 

 canal leading into a sac below, which contains a single germ or 

 embryonal cell. Fertilization is considered to take place by the 

 ciliated spermatozoids contained in the microspores {fig. 1111, c), 

 passing down the canal of the archegonium and coming into con- 



Fig. 1111. 



Fig. 1112. 



Fig. 1113. 



ooo ®, 



© @ 



Fio. 1111. Small spore, pollen-spore, or microspore, of a species of Selagi- 

 nella, bursting and discharging small sperm-ceils, c, iu which spermato- 

 zoids are contained. Fig. 1112. Large spore, macrospore, or megaspore, 



of a species of Selaginella. The outer coat of the spore has been removed 

 to show the entire inner coat, with the young prothallium, p, at the 



upper end. Fig. 1113. Vertical section of a portion of the prothallium 



of the above in a more advanced state, showing the archegonia. a. 

 Archegonium, in which the pseudo-embryo, e, has been developed 

 from the germ-cell it contained, by contact with the spermatozoids. 

 This embryo, by the growth of the suspensor, is forced downwards 

 and imbedded in the upper part of the cellular mass of the spore-sac. 



tact with the germ-cell. This cell then grows by cell-division 

 and forms a pseudo-embryo {fig. 1113, e), and ultimately pro- 

 duces a new leafy sporangiferous stem. The LycopodiacecB pre- 

 sent, on the whole, the highest type of Cryptogamic vegeta- 

 tion. 



5. MarsileacecB or Pepperworts. — The two reproductive organs 

 of this order are generally distinguished as antheridia {figs. 794 



