68 



FKlVm.lZ,VT10N AND FEUrr-FOHMA'MON IN OHVrTUUAMvS, 



ooutiu't At lonjfth tho top of tho nubhoi-idium opous; (.ho loiiao coIIh m-o disohfti-ged 

 into tho 8uri"ouuding water dorivod fwiu rain or dow, and fixmi oucl> of tlioui is set 

 l'n>o a, spirally -coiled spermatoEoid fivrninhod »V8 ii'gavdn its aid.orior l\alf with 

 bristlinii" cilia (see vol. i. p. 29, lig. 7 "). Tho spoi-uuitonoids uuuiilVntly dii-eot their 

 oourao to an anipliigoninni a.s tlioy whirl aliunt in tlie wator. Moiuiwhile tho tjiuml- 

 coUs of nook of tho aiuphigvuiivuu havo baen partially oouvortod into umoilago; bouio 

 nmoilagv is disoharged into tlio onvinniing water, ami it Hooms that oouoomitaatly 

 with this orj^-anio acids havo beon o\ulvod iu tho wg'ion of tho ttiuphigoaium, whidi 

 exoi-ciso an attractive influence on the uporniatonoidH. What is known as a i'ttot ia 

 that the sporumtoaoids aooumulate in tlii^s mucilaginous mass aud also peuotiuto 

 through the slimy substance loft behind in tho canal of tho amphigonial nook. 

 Thus they roaoh the ooplasm which is hiddon in tho oogonium at tho bottom 

 of tho fruit-rudiment. As it has ropoatodly boon obsorvod that spermatoaoids 

 make their way into tho ooplasm and thoro disappear, we may assume tluit 

 tho delicate onvolopo of the ooplast is pioi-ood by tho spormatoaoid, and tlmt 

 thereupon a coalesconco between tho two kinds of protoplasm takos place (o/. also 

 figs. 3461. •■'•».*). 



'Pho fortilized ooplasm now subdivides into sovoral colls with partition-walls 

 inserted between thom, and thus is pi-oducod a multicoUular embryo which roniaiiiN 

 embedded in the unaltered aniphigonium. This structure, though soarooly dillbring 

 at all from the fruit-rudiment, must bo considered as a fruit. Aftor a short poriod 

 of rest tho embryo germinates, and tho now gonoration, which graduallj' uiakes its 

 appearance as stem, roots, and fronds emerging from tho embryo, oontinuoH for a 

 sliort time to receive its food-stuffs through tho mediation of tho parental pro- 

 thallium. At length, when tho new gonoration has grown suffloiontly strong, and 

 is capable of taking up f<ii)d-stuffs directly from the surrounding air and Hoil, and 

 of transforming them into constructive materials, tho assistance of tho prothivllium 

 becomes superfluous. Tho prothallium then withei-s, and by tho tiirio tho sporo- 

 gonous fronds havo developed it has vanished, and no trace of it romains. 



The Horse-tails (EquisetaooBa) havo, in the main, tho Haino foaturos as tho Fems 

 just described as typical of tho Vascular Cryptogams in all that rolatos to tho forms 

 of prothallium, antlioridia, and fruit-rndiments. Tho protiiallium produocMl from 

 the spore is at first delicate and ribbon-shapod, but later becomes multifariously 

 lobed, and in foi'm recalls tho thallus of cortaiu Livorworts, or sometiines ovon 

 resembles a little curled foliage-leaf. In most species antlioridia and fruit- 

 rudiments grow on difforent prothallia. Where this is not tho caso, fertilization 

 of the ooplasm by spermatoplasm arising from the same individual is rendered 

 impossible by means of a disparity between tho organs oonoornod in rospoct of 

 tho time at which they mature. 'I'ho prothallia wliioli give rise to antlioridia 

 are always much smaller than those which produce tho fruit-rudiments. The 

 antheridia develop from superficial cells at the ond or on tho margin of tlio lobato 

 prothallium, whilst the fruit-rudiments, on tho othor hand, aro derivod from super- 

 ficial coUh in the recessos between tho lobes (soo (ig. 1()0'), 'Hio spermatozoids 



