392 SUMMARY OF CUBRENT RESEARCHES RELATING TO 



dasycarpum), 3 ft. 11^ in. in circumference, there appeared to be a 

 contraction of l-8th in. In dead wood soaked in water tliere was an 

 evident expansion, and the cleavage with exjilosion, noted in the case 

 of forest-trees in high northern regions, may result from the freezing 

 of liquid in the centre of less vital parts of the trunks. In some 

 hardy succulents, however, instead of expansion under frost, there was 

 a marked contraction. The joints or sections of stem in Opuntia 

 Bajinesquei and allied species shrink remarkably with the lowering of 

 the temperature, so that the whole surface in winter is very much 

 wrinkled. Assuming as a fact that the liquids in plants which are 

 known to endure frost without injury do not congeal, it might be 

 a question as to what power supplied the successful resistance. It was 

 probably a vital power, for the sap of plants, after it was drawn from 

 them, congealed easily. In the large maple tree already referred to, 

 the juices not solidified in the tree exude from the wounded portion 

 and then freeze, hanging from the trees as icicles, often 6 in. long. 



Influence of Electricity on Vegetation.* — M. Macagno has 

 experimented near Palermo iipon the influence of atmospheric elec- 

 tricity on the growth of grape vines. Sixteen feet were submitted to 

 the action of an electric current, by means of a copper wire inserted 

 by a platinum point in the extremity of a fruit-bearing branch, while 

 another wire connected the branch at its origin with the soil. The 

 experiment lasted from April to September. The wood of the branches 

 which were experimented upon contained less potash and other 

 mineral matters than the rest of the vine, but the leaves had an 

 excess of potash under the form of bitartrate ; the grapes collected 

 from the electrized branches furnished more must, contained more 

 glucose, and were less acid. 



B. CRYPTO GAMIA. 



Cryptogamia Vascularia. 



Male Prothallium of Equisetum.t — D. H. Campbell describes 

 the development from the spore of the male prothallium of Equisetum 

 arvense. "When the spores are sown under glass or on damp earth, 

 they germinate almost immediately. They first put out a nearly 

 colourless rhizoid, the body of the spore then dividing into two cells by 

 a longitudinal septum. Directly after germination, the chlorophyll 

 begins to collect into distinct chlorophyll-bodies ; the mode of sub- 

 sequent cell-division varies considerably ; some of the prothallia 

 showing a tendency to branch quite early. Some of the prothallia 

 send out a second rhizoid from one of the lower cells ; finally they 

 become somewhat club-shaped. The first mature antherozoids were 

 observed nearly six weeks after the sowing of the sj^ores. 



The structure of the antheridium is extremely simple, consisting 

 simply of a cavity or excavation in the end of a branch of the pro- 

 thallium. It commences by a concentration of protoplasm at the spot, 



* ' Lps Mondes.' See Journ. Frankl. Institute, cxv. (1883) p. 311. 

 + Amer. Natural, xvii. (1883; pp. 10-15 (2 pis.). 



