'60 BEPOET— 1892. 



». Remarks on a Series of Extinct Birds of New Zealand, recently discovered. 



By H. O. Forbes, F.Z.S. 



6. Natural Eelatiovs lettveen Temperature and Protoijlasmic Movements. 

 By Jas. Clakk, M.A., Ph.D. 



For every vegetable cell showing streaming movement in the protoplasm there 

 is a minimum temperature below which all movement ceases, an optimum at 

 which the rapidity of the streaming is greatest, and a maximum beyond which 

 movement is impossible. Of these the minimum is of greatest practical 

 importance. 



Although we possess many isolated determinations of the minima for various 

 plants, no attempt has yet been made to cai'ry out a series of systematic observa- 

 tions on the subject. 



As might have been expected, the minimum varies greatly according to the 

 nature and the general surroundings of the plant. Thus, of eight species collected 

 on the "\'incent pyramid of Monte liosa at a height of over 10,000 feet all showed 

 streaming movement in the parenchyma of the stem at O'^ C. ; of six collected at a 

 similar heigbt on the Aletschhorn five gave identical results, the exception being 

 Linaria alpina. The plants, too, that flower on the lower Swiss Alps immediately 

 on the retreat of the snows in spring — Soldanella alpina, S. j)usilla, Crocus 

 verna, I'rimula iiitegvifolia, Alcheniilla iK'niaphyllea, &c. — all exhibit decided 

 protoplasmic movements at 0° C. Similar results are obtained from winter 

 seedlings of SteUaria viedia, Cerastium triviale, and Seyiecio indgaris in England. 

 The stem parenchj-ma of most of our farm crops gives a minimum of about 5° C ; 

 for sainfoin {Onobrychis sativa), Lupines, Indian corn, the minimum is from 8° C. 

 to 11° C. ; for tomatoes about 14° C. ; and for the majority of stove plants 18° C. 

 or over. 



Such minima are not constant for the same species, but vary according to the 

 conditions under which the individual has actually been growing. Cochlearia 

 officinalis, growing on our sea coasts, usually gives a minimum of 5° C to 7° C, 

 whereas the minimum for specimens collected on the Ilorneckalp in the Justisthal 

 was about 1° 0. Asphodelus nlbus, on the Riederhorn and at Rawyl in Switzer- 

 land, shows a minimum of 2° C, and in its Mediterranean habitats of 7° C. to 

 11° C. 



The minimum for the stem parenchyma of Soldnnella alpina is usually 0° C. or 

 lower, but there is a variety found on the lower slopes of the liigi in which the 

 minimum lies between 5° C. and 7° C. 



Seeds of Androsace ylacialis, Anemone venialis, Cherlena sedoides, Draba 

 WaMenberyii, Gentiana bavarica, var. ivibricata, G. nana, Sa.vifraga bryoides, &c., 

 collected at a height of 8,000 feet or more, produced plants in the botanical 

 gardens at Tiibingen and in the vicinity of the Lake of Geneva, in which the 

 minima were from 4° G. to 12° C. higher than in the parent plants. Seeds from 

 these garden-grown plants, though capable of germinating freely on the plain, 

 rarely did so when sown in the habitats of their mountain ancestors. Specimens 

 of Potamogeton marinus from Lake Fully (7,000 feet) showed streaming movement 

 in the leaf at 0° G.,but, on being kept in the botanical gardens at Tiibingen for six 

 months, showed a minimum of 7° C. 



In the marshes of the Jura, where, in consequence of local conditions, the 

 average temperature is very much lower than that of the surrounding country, 

 the minima for protoplasmic movements in the stem, and particularly the root, are 

 very low. In the parenchyma of the roots of Gentiana pneumonanthe and Swertia 

 perennis, for instance, circulation of the protoplasm was well defined at 0° G., and 

 in the upper part of the stem was just visible at 2° C. 



The minimum for the cells of the root is, as a rule, lower than for those of the 

 stem and leaves, the diflerence in some bog plants examined being as much 

 as 8° C. 



