66 



VASCULAR CRYPTOGAMS 



leptophylla (Desv.) the prothallium is many-lobed, and the archegones 

 and antherids are produced on separate conical tuber-hke outgrowths 



from its under side, which penetrate 

 into the soil, where they are perennial, 

 and may give birth by budding to new 

 prothallia, while the sporophyte gene- 

 ration is annual. The prothallium is 

 occasionally, in the Hymenophyllaceas, 

 reduced to a single row of cells ter- 

 j*/?'" °^^^>^*^^:^^^b3$^ minating in an antherid, or even to a 



single cell. Campbell has detected 

 continuity of protoplasm in the cells of 

 the prothaUium of Struthiopteris ger- 

 manica (L.). In the Osmundacese the 

 prothallium springs directly from the 

 spore without any intermediate proto- 

 neme, a plate of cells being formed on 

 Fig. 43.— Under side of prothallium of germination by longitudinal and trans- 



Aneimia Phyllitidis Sw. sk, cushion, ^... , ^ ,. ■i- 



with archegones ;«, antherids aAdrhlzoids VCrSC dlVlSlOnS ; the firSt rhlZOld IS 



(X25). (After Bauke.) fomicd out of a postcrior ccll. The rib- 



bon-shaped prothallium of Osmunda (L.) is characterised by the presence 

 of a midrib composed of several layers of cells running along its whole 



length. The arche- 

 gones are produced 

 on the under surface 

 on this midrib ; the 

 antherids either on 

 the margin or on the 

 under surface with 

 the exception of the 

 midrib. An approach 

 towards a higher type 

 of organisation is 

 indicated by the 

 tendency of the pro- 

 thallium to become 

 dioecious in the 

 Osmundaceae, and in 

 Struthiopteris (L.). 

 All the spores from 

 the same sporange 

 sometimes produce male prothallia, i.e. such as bear antherids only, the 



jTjQ ..^ — Antherid of Adiantnm capilbis-Veneris L., in different 

 stages. /, prothallium; a, antherid ; 5, antherozoids ; b, vesicle 

 with starch-grains ( x 500). 



