DUNEDIN NATURALISTS’ FIELD CLUB.

Otago Witness, Issue 3828, 26 July 1927, Page 16

DUNEDIN NATURALISTS’ FIELD CLUB.

SATURDAY’S EXCURSION. The purpose of the afternoon’s excursion on Saturday last was to observe the disposition of the sedimentary rocks around Dunedin. The club travelled by Corporation bus along the Main South Road to Abbotsford, stopping at various points on the journey to examine the outcrops which there occurred. A chart had been prepared to show the sequence to be expected, and they . were -On top of Lookout Point, volcanic rocks; beside the road as it descended into Burnside. Caversham sandstone; at Green Island, first the marl surmounted by a dark band of greens in the Cement Company’s quarry, and then loose sands in a quarry a little further on. It was noted in these two outcrops that the strata were dipping gently to the east. Then at Abbotsford was seen the mudstone and finally in Fernhill Creek were seen the coal seams and associated sands resting on the fundamental schist. The general characteristics of these sediments, their ages, and conditions of depositions and relations to other parts of the country were discussed. A visit was then paid to the Kaikorai lagoons, where the raised beaches were noted and their origin explained. The partv was under the leadership of Mr H. S. Tily. INDOOR MEETING. At the indoor meeting held on Monday evening Dr Holloway gave a very interesting and instructive lecture on lichens. The lecturer stated that lichens belonged to those simpler forms of plants know-n as Thallophytcs—that was to say, plants which had an undifferentiated or unorganised plant bodv. They grew chiefly on the bark of trees, or on old palings, walls, etc. In some instances they presented a dry, shrivelled, more or less lifeless appearance and sometimes they appeared as a mere colouring on boulders as if painted on. They were distributed in all parts oi the world. The pulverulent species were the first plants to clothe the bare rocks of newly-formed islands in the midst ot the ocean. Foliaceous lichens followed these, then mosses and liverworts. They also formed a considerable proportion ot the vegetation of tae polar regions and ot mountain tops. Dr Hollow-ay. however, roused the interest of his audience by stating that lichens were of the vegetable kingdom, an ■ xtraordinary phenomenon, being dual plants consisting of a fungus and an algae. It was a case of symbiosis, two plants living together for a social benefit. For a long time this was not generally known. In analysing the plant, early scientists saw- the algae cells, but thought they were reproductory organs. Even yet there were quite a number of lichenologists who doubted the fact, and American botanists said that it was just another instance of fungus being parasitic, this time a menial case —i.c., fungus para-

sitic on algae. Dr Holloway, however, preferred to deal with it as a case of symbiosis, of which there were many instances in the plant and animal kingdoms. Instances of symbiosis were *ven known in animals and plants. The mutual benefits derived were stated to be, fist, the fungus gave protection to the algae and also handed on to the algae salts a.id water derived from the soil, while in turn the algae passed on sugar food to the fungus. Lichens had actually been built up in laboratories by man, which fact was straight-out evidence that there were two plants. Dr Holloway stated that New Zealand lichens were bv no means thoroughly known, hence he would attempt to give only a general account of the life history of a few typical New Zealand genera. In some lichens the fungus threads permeated throughout all the body and in others it was in lawyers. By these means they were classified as — (i) stratified, (2) unstratified: 95 per cent, belonged to the latter. They were again divided into three main groups: (1) Crustaceous lichens, growing on boulders (numerou.) ; (2) foliose lichens, flat, leafy; (3) fruticose lichens, erect growing. The methods of reproduction and the reproductory organs of these truly wonderful plants were also dealt with, the latter being illustrated with lantern slides. Several specimens of local species were then shown and their natural habitats stated. Among the more noteworthy specimens was one from Maungatna. pure white and very pretty, known as the coral lichen (Lecanora —crustaceous group). also another (Urnea), resembling an old man’s beard and growing ot. trees, and Uladonia (closely related to the reindeer moss of the Arctic region), both of the fruticose grouns. A very hearty vote of thanks was accorded Dr Holloway for his very interesting lecture.