ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 77 



arises in tvo ways : — in S. rupestris from the single hypodermal cell 

 formed by the archespore being divided by a periclinal wall, thus pro- 

 ducing a wall and a sporogenous cell ; or by the archespore dividing into 

 four cells by a periclinal wall, the two hypodermal cells thus formed 

 developing the sporogenous tissue. The tapete is formed in part from 

 the sporogenous cells near the exterior of the mass, in part from 

 adjacent vegetative cells. 



The micro- and megasporanges are indistinguishable before the 

 spore-mother-cells are differentiated. The normal number of meg;tspores 

 in a sporange is 4 ; but in S. rupestris only 2, or even only 1, may reach 

 maturity. In both species the megaspore has three distinct coats, — 

 exospore, mesospore, and endospore. The female oophyte is formed by 

 free-cell-division of the megaspore, the nuclei dividing by indirect 

 division. The microspores develop in a manner analogous to the 

 megaspores. The male oophyte (of S. apus) consists of a single prothal- 

 lial cell and a mass of potential sperm-cells ; there is no antherid, nor 

 is there a wall separating the prothallial from the sperm-cells. In both 

 species the spermatozoid is a spirally coiled body, on which no cilia were 

 detected. Both kinds of sporange open by definite lines of dehiscence. 

 Fertilisation occurs, in both species, while the spores are unshed and the 

 sporanges are still attached to the strobile. 



Prothallus of Ophioglossum, Helminthostachys, and Psilotum. * — 

 Dr. W. H. Lang gives a preliminary account of the prothallus of these 

 genera of Vascular Cryptogams found in the Malay Peninsula and 

 Ceylon. 



Ophioglossum pendulum. The very young prothallus is button-shaped. 

 A close covering of paraphyses extends uninterruptedly from just above 

 the base over the whole surface. The youngest prothalli are radially 

 symmetrical. Subsequently a more active growth takes place at two 

 or three points on the margin ; a corresponding number of cylindrical 

 branches arise, and the prothallus becomes irregularly star-shaped ; the 

 larger prothalli consist of branches radiating in all directions. From 

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

 of the branch is covered with short wide unicallular paraphyses, 

 which are absent only above the sexual organs. The prothalli are 

 monoecious, archegones and antherids being found close together on the 

 same branch. The surface projects very slightly above the large sunken 

 antherid ; the neck of the archegone, which, as seen from above, con- 

 sists of four rows of cells, hardly projects from the prothallus. Rhizoids 

 were not seen on any of the prothalli examined. An endophytic fungus 

 occupies a middle zone of tissue in all the branches. 



Helminthostachys zeylanica. The prothalli were found at a depth of 

 about three inches. The youngest prothallus obtained was a short 

 cylindrical body a little over ^ in. in length ; the lower end bore a number 

 of short rhizoids ; the apex was bluntly conical. The lower vegetative 

 region increases in size and becomes lobod, while the antherids are confined 

 to the cylindrical upper portion. Seven of the young prothalli found were 

 male, two female. The female prothalli were stouter and more lobed 

 than the male ones ; but both antherids and archegones might occur on the 



* Proc. Koy. Soc, lxviii. (1901) pp. 405-9 (3 figs.). 



