Page:Proceedings of the Royal Society of London Vol 60.djvu/280

254 Scolopendrium vulgare, L., var. ramulosissimum, I — The cultures of this fern were m ade in the m anner already described for Lastrcea dilatata. The spores were obtained from a plant grown in the open air in the Royal Gardens, Kew.

The prothalli were at first heart-shaped, and on many of them normally produced embryos developed. No fu rth er changes ensued in those on which young plants were present, and they soon became colourless and died. In those which had rem ained unfertilised, however, the apex continued directly into a cylindrical process, which was of considerable thickness, and in some cases attained a length of 5 mm. The lateral portions of the prothallus showed no further growth, and became in time brown or colourless appendages to the base of the cylindrical process. On the process were numerous archegonia, and its prothallial nature was still further shown by the presence, in some instances, of thin lobes of tissue, which generally bore antheridia. Sections through the process in this stage show that the archegonia are norm ally formed, and reach almost to the apex, and that tracheides are absent from the tissue. The archegonia are capable of fertilisation, for in some instances normally produced embryos were found.

After the process has in this manner attained a greater or less length, its tip becomes yellowish, contrasting with the deep green colour of the region behind. N ear the apex ram enta develope, which soon completely clothe the tip of the process and render it white and conspicuous. Archegonia are present to ju st below the ramenta. Longitudinal sections at th is stage show th at one or two small elevations corresponding to the rudiments of the apex of the stem, and the first leaf of the sporophyte have been formed. Beneath the broad tip a flat mass of small m eristem atic cells extends; the m eristem atic tissue is continuous with that of the stem and leaf apices, but, on passing away from these, is separated by several layers of large, nonm eristem atic cells from the surface. In a slightly older stage the stem apex has become conical, and a num ber of leaves have formed which are circinately curved, and form a bud clothed with ramenta. In the m eristem atic mass num erous tracheides have been developed. One large group is central in position, and extends to the limit between prothallial and sporophytic tissue, while others are found beneath the bases of the leaves, and are in continuity with their procambial strands. The apex of the stem is occupied by an initial cell, the relation of which to the initial cell or cells of the apex of the process has not yet been traced. The young sporophyte appears to be a direct continuation of the process. It is possible that some of