The Royal Society, London. 257 



In slightly older prothalli, seen from above, the circular outline is lost, 

 owing to the inore active growth of two or three points on the margin. 

 This continues, and there thus arise a corresponding number of cylindrical 

 branches, the prothallus becoming irregularly star-shaped. At first the 

 branches spread out in a horizontal plane, though with a slight upward 

 tendency. But when the branches themselves subdivide all Suggestion of 

 this secondary dorsiventrality is lost, and the larger prothalli consist of 

 branches radiating in all directions into the humus. 



From a short distance behind the smooth, bluntly conical apex the 

 surface of the brauch is covered with short, wide, unicellular paraphyses 

 analogous to those known in prothalli of Lycopodium Phlegma ria. 

 These are only absent above the sexual organs. 



The prothalli are monoecious, antheridia and archegonia being found 

 close together on the same branch. The surface projects very slightly 

 above the large sunken antheridium ; the neck of the archegonium, which, 

 as seen from above, is composed of four rows of cells, hardly projects 

 from the prothallus. The sexual organs thus resemble those of 

 0. pedunculosum, as described by Mettenius. 



Rhizoids have not been seen on any of the numerous prothalli 

 examined. An endophytic fungus occupies a middle zone of tissue in 

 all the branches, the superficial layers and a central core of cells being 

 free from it. 



Helminthostachys zeylanica. 



The prothalli of this plant were also found in the Barrawa Forest 

 Reserve, a low-lying jungle subject to frequent floods. Young plants 

 still attached to the prothallus were fairly abundant in certain spots, 

 and, by searching in the rotting leaf mould around, prothalli of various 

 ages were obtained. The prothalli were found at a depth of about 

 2 inches. 



The youngest prothallus obtained was a short cylindrical body a 

 little over one-sixteenth of an inch in length. The lower end was darker 

 in tint and bore a number of short rhizoids, while above this, where the 

 antheridia were situated, the surface was of a lighter colour. The apex 

 itself was bluntly conical and almost white. In slightly larger prothalli 

 the contrast between these two regions was more strongly marked. The 

 lower, vegetative region increases in size and becomes lobed, while the 

 antheridia are confined to the cylindrical upper portion, which continues 

 to increase in length. This latter region appears to be longer and the 

 lobed basal part relatively less developed in prothalli which bear the 

 antheridia. Seven of the young prothalli found were male ; the other 

 two bore archegonia only. These female prothalli were stouter and more 

 lobed than the male ones and the diameter of the short apical region, 

 on the surface of which the archegonia were situated, was almost the 

 same as that of the vegetative region. There thus appears to be a 

 partial sexual differentiation in the prothalli of Helminthostachys, 

 but both antheridia and archegonia may occur on the same prothallus, as 

 some of the latter attached to young plants have shown. The antheridia 

 are large and offen closely crowded together. They hardly project from 

 the surface, the wall being only slightly convex. The archegonial neck, 



Botan. Oentralbl. Bd. LXXXVII 1901. 17 



