ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 
65 
piadefe ; tlie leaves are often greatly reduced, the chlorencliyme of the 
stem performing the function of assimilation ; though some species of 
Euphorbia have quite normal leaves. In some species both of Euphorbia 
and Mesembryanthemum; the growing point is protected against desicca- 
tion by being deeply imbedded in the tissue of the stem. Many Cactacem 
have brittle branches which readily break off and are scattered by the 
wind ; the seeds of the epiphytic Bhipsalis Cassytha are disseminated in 
the same way as those of the mistletoe. In some species, as Cereus 
tuberosus and Euphorbia tuberosa, the storage of water takes j)lace in the 
root. The ribs of many Cactaceae are the result of the coalescence of 
rows of papilige. 
Vegetation of Mud-Banks.* — Prof. K. Goebel describes the pecu- 
liarities of the vegetation of mangrove-swamps. The air-roots serve 
simply for support, the nutriment being absorbed through the mud-roots. 
A similar germination of the seeds while still within the seed-vessel 
to that of Rhizophora takes place also in Aegiceras (Myrsinaceae), Avi- 
cennia (Verbenaceae), and in Crinum asiaticum (Amaryllidem) ; and the 
phenomenon may be compared to that in the epiphytic species of 
Hymenophyllum, Pellia, and Fegatella, whore the first stages of germina- 
tion take place within the sporange or sporogone. The aerial roots of 
Sonneratia and Avicennia'\ which grow erect out of the mud are 
respiratory organs. 
Temperature of Trees.J — Mr. H. L. Eussell has conducted certain 
experiments upon the temperature of trees. Holes one-half inch in 
diameter were bored into the trees at equal heights from the ground, 
and thermometers were inserted in the borings so that the base of the 
bulb came in contact with the wood ; the sj^ace about the thermometer 
was packed tightly with ■ cotton- wool. An experiment made upon 
Carya alba gave the following result. The temperature of the tree, as 
a general ru’e, ranged higher than the outside with two or three excep- 
tions, when the air temperature was higher during the warmer portions 
of tlie day. Comparative observations were made with the pine, larch, 
oak, poplar, and outside air, and in all cases tbe temperature of the pine 
was found to be considerably lower than any of the remainder (except 
during the latter part of the night and early morning). Presumably 
the thick coating of foliage has a tendency to prevent absorption of heat 
by the trunk. The conclusion arrived at by the author is that the 
direct absorption of heat is the main cause of the higher temperature 
of trees, and that it is largely dependent upon the character of the bark. 
Cotton Fibre.§ — Mr. T. Pray describes the structure of various 
cotton fibres. Fibres of the best Pernambuco cotton will be found to 
be rather fiat and of the nature of narrow tape. The edges are not 
thickened, and there is little or no spirality in the fibres. The oil- 
deposits are few, and not very marked. Upland cotton is not strong 
and robust in appearance ; the fibres are weak in their outline, not very 
well thickened on the edges, but the spirality is more noticeable. There 
* Pflanzen-biol. Schild., Pt. i., Marburg, 1889, pp. 111-46 (1 pi. and 4 figs.), 
t Cf. this Journal, 1887, p. HI. X ddot. Gazette, xiv. (1889) pp. 216-22 (1 pi.). 
§ Jouin. Franklin Inst., cxxviii. (1889) pp. 241-57. 
1890. P 
