212 



KNOWLEDGE 



[Septembeb 1, 1898. 



produced. This becomes thicker in the centre owing to 

 division of cells in a horizontal direction ; and from the 

 under side are developed slender root-hairs or rhizoids, 

 which serve both to anchor the plant to the soil and to 

 collect food material therefrom. 



Thus the cell-plate is able to lead an independent 

 existence, feeding itself from the air and the soil like 

 other green land plants. Yet it shows no tendency to 

 differentiate into root, stem, and leaf, or to acquire any of 

 the characteristics of a fern. Longer observation will 

 show also that it does not continue to increase in size ; 

 many will dry up and disappear, but from some of them 

 new green shoots will be seen to rise growing upward from 



by dark spots distributed more especially over two 

 regions. The more conspicuous -are small round bodies 

 scattered among the bases of the root-hairs ; while 

 another group occurs above, round the indentation at the 

 apex. 



It will be found quite possible to get a good idea of the 

 form and nature of these structures by carefully focussing 

 the microscope, or even by dissecting them out with 

 needles ; but it is far preferable to harden some of the 

 plants in spirit and then cut thin sections through them. 

 The latter group referred to will be found to have all the 

 essential characteristics of Archegonia, a typical egg cell 

 lying in a rounded cavity, and above it a " neck " composed 



A. — The Fern Spore, n. — Germination of the same, producing the young Oophyte or Prothallus. c. — One of the Cells 

 of the Prothallus, showing the Protoplasmic Contents, with Nucleus, Vacuoles, and Chlorophyll bodies. D. — The 

 Prothallus, seen from the under side. The small round bodies among the root-hairs toward the apex are Anfheridia ; those 

 below the notch arc the Archegonia. E. — An Antheridium as seen in Section, with the mass of developing Antherozoids n-ithin. 

 F.— One of the Antherozoids (or Sperniatozoids) set free. (Highly magnified.) o.— An Archegonimn ready for Fertilization. 

 H. — A withered Prothallus, witli a young Fern Plant (Sporophyte) growing from it. I.—Sporophgte of Asplenium trichomanes, 

 showing the creeping Stem (Rhizome) and young Fronds rising behind its apical growing point. J. K. — Younger and older 

 Pinnie of the Frond, showing the Sori on tlieir under surface, l. — Section througli a Pinna and Sorus, showing the Sporangia 

 in different stages of development, partly covered by the Indusinm. M. — A ripe Sporangium with enclosed Spores. >'. — A 

 burst Sjjorangium discharging the Spores. 



their surface. These are evidently new structures, not 

 further growths, since the heart-shaped cell-plate still 

 remains, though shrinking and withering round their 

 base. 



The explanation of these phenomena can only be arrived 

 at by a closer study under the microscope. 



If a medium-sized disc, one about a quarter of an 

 inch across, is mounted in water and examined with a 

 moderate magnifying power, it will be seen that the 

 regularity of the cell arrangement is sometimes broken 



of several rows oi cells surrounding a central passage. 

 The wall of the chamber round the egg cell is not so 

 distinct as in the moss, since the whole base of the struc- 

 ture is here embedded in surrounding tissues ; the neck is 

 also much shorter and wider, but these are mere detaUa, 

 the organ is evidently an Arche;ioniuni. 



That the round bodies occurring among the rhizoids are 

 similarly true Antheridin may be readily proved if one of 

 the darker-coloured riper ones is selected and burst by 

 light pressure on the cover glass. A mass of small cells 



