TRANSACTIONS OF SECTION K. 1019 
MONDAY, SEPTEMBER 21. 
The following Papers were read :— 
1. On the Number of Spores in Sporangia. 
By Professor F. O. Bower, /.2.S. 
2. The Polymorphism of the Green Alge, and the Principles of their Evolu- 
tion. By R. Cuopat, Professor of Botany in the University of Geneva. 
The paper treats of the following subjects: Primitive and Nodal Types; Pre- 
ponderance of Fluctuating Characters in the different Series; Specialisation of 
Characters and their Fixation; Sexuality: its Origin and Tendencies; supposed 
Relations with the Archegoniate. 
3. On some Peculiar Cases of Apogamous Reproduction in Ferns. By 
Wituiam H. Lane, IB., B.Sc., Robert Donaldson Scholar, Glasgow 
Unwwersity. 
In order to ascertain to what extent apogamy in Nephrodium filiz-mas, Desv., 
is correlated with the cresting of the fern plant, from which the spores were de- 
rived, cultures of normal and crested forms were made. Of the three cultures of 
normal forms one was unsuccessful ; one of the others was exclusively apogamous, 
while the other has, as yet, reproduced in the ordinary way. Seven crested varie- 
ties were sown ; five of these were apogamous and the other two normal. Three 
of the crested varieties were known with certainty to be wild finds; two of these 
were apogamous. From these results it appears that apogamy in WN. filiz-mas 
stands in no definite relation to cresting. When the ferns sown were divided into 
Wollaston’s species, NV. filix mas, N. pseudo-mas, and N. propinquwm, it was found 
that all the varieties of the two former were apogamous, while both normal and 
crested forms of NV. propinguum were normally reproduced. The basis of observa- 
tion is, however, too limited to allow of any generai conclusion being drawn as to 
the constancy of this difference. 
Cultures were also made of crested varieties of other species. In all in which 
young plants were produced their development was at first normal. After the 
cultures had continued for nine months young plants, developed apogamously, 
were found in Scolopendrium vulgare, Athyrium filix feemina and Aspidium aculea- 
tum, var. angulare. It is impossible at present to decide how far the result can be 
ascribed to cresting of the parent plant. Possibly the prolonged cultivation of 
unfertilised prothalli is the more important factor in these cases, the cresting aiding 
as a predisposing cause. 
Unfertilised prothalli of Scolopendrium vulgare formed a cylindrical, fleshy 
prolongation of the midrib, the tip of which became in time covered with ramenta, 
and was continued directly as the axis of the young sporophyte. Archegonia were 
present just below the ramenta. 
In some prothalli of a fern from Mr. Druery’s collection, which was labelled 
Lastrea dilatata, vay. cristato-gracilis, a similar prolongation of the median region 
was found. Upon this sporangia were borne, sometimes singly, in other cases 
grouped together so as to resemble a sorus. The sporangia had a well-developed 
annulus which sometimes showed the characteristic reddish-brown thickenings of 
the wall. The prolongation on which the spcrangia were situated bore archegonia 
and antheridia which sometimes intervened between two groups of sporangia. Its 
prothallial nature was, therefore, beyond doubt. The sporangia were borne on 
prothalli on which no trace of a young sporophyte could be detected. 
