7^ 



OPHIOGLOSSACEAE 



[CH. 



lO cm. below the surface of the soil, and is a flattened tuberous body as 

 much as 20 mm. in length: it possesses sluggish apical growth, and maybe 

 lobed at the tip. It is pale to brownish in colour, and bears transient hairs, 

 which offer entrance to the symbiotic fungus. Sections show that the 

 infected region comprises the greater part of the central tissue leaving the 

 periphery free. On the uninfected tissue, which is thicker at the upper 

 flattened surface and includes the meristematic region, the sexual organs are 

 borne. The antheridia are formed first near to the median line, while the 

 archegonia appear later usually upon the flanks of the convex median ridge. 

 It has been thought that this form and the arrangement of the sexual 

 organs are convenient biologically, in presenting an upward face to rain 

 soaking into the soil, and thus washing the sperms from the higher-lying 



Fig. 376. Development of the antheridium of Botrychhcm virgi/iianum (after 

 Campbell). A-D, longitudinal sections of young antheridia (X240); E-H, 

 transverse sections; F, G, show only the young spermatocytes; H, surface view, 

 opercular cell, 0; I, section of two ripe antheridia ( x 60). 



antheridia to the archegonia below. The antheridia are deeply sunk, pro- 

 jecting only slightly when mature from the surface of the prothallus (Fig. 

 376). Each originates from a single cell, which divides periclinally {A) to 

 form the wall and the fertile tissue. The spermatocytes are very numerous, 

 and the dehiscence takes place where the wall remains one cell thick, and 

 thus one definite opercular cell only is destroyed in the process. In 

 B. Lwiaria several such opercula may be seen (Vol. I, Fig. 283, A). The 

 spermatozoid has about \\ coils, and resembles that of Ferns and Equisetum, 

 having numerous cilia. The archegonia are clearly of the Fern-like type: 

 each originates by a regular Fern-segmentation (Fig. 377, A, B, C). The 

 subsequent divisions in the central cell and in the cover-cell agree very 

 closely with those in OpJiioglossiun ; but the neck-cells are more numerous, 

 and at maturity the neck projects much more strongly. There may be seven 



