1894. NOTES AND COMMENTS. 7 



and the African coast, is sufficient explanation of its early introduc- 

 tion into the latter region. 



Mr. Henslow goes on to describe the method of multipHcation 

 in the northern hemisphere. In Malta the plant is ubiquitous, carpet- 

 ing the roadsides as well as all the exposed open ground around 

 Valetta, and insinuating itself between the loose stones of the walls? 

 appearing at the surface like a green fringe around each. It covers 

 the tops of the walls in many places, and the lofty fortifications ; it 

 forms luxuriant borders to the fields, and also invades cultivated soil? 

 so that, where weeds are not uprooted, a field will look as yellow as 

 an English meadow with buttercups. It is propagated entirely by 

 bulbs. A large plant growing among loose, stony debris, if dug up 

 in January, will be found to possess a long tapering stem, throwing off 

 thread-like lateral roots, and bearing minute leaf-scales with small 

 white bulbils at intervals, as well as several larger ones at the crown, 

 below the cluster of leaves. The fine thread-like rhizome extends 

 downwards, sometimes for more than a foot, and grows from a bulb 

 of last season. In many cases when the plant grows as above, the 

 stem proceeds further downwards like a thread ; but after a certain 

 distance suddenly increases in diameter, forming a short rod-like 

 structure about i^ to 2 inches long, with a bulb at the end. This 

 explains how it can reach great depths from which new plants arise in 

 a subsequent season. On plants growing luxuriantly, runners above 

 ground may be formed, which also produce bulbs at the nodes, so that 

 a number of young plants arise at a short distance from the site of 

 the parent. 



The author remarks that the extensive vegetative reproduction 

 oi Oxalis cevnna in the Mediterranean, like that of Elodea Canadensis in 

 this country, is a strong argument against the assumption of the 

 necessity of cross-fertilisation to ensure a vigorous offspring. Change 

 of hemisphere has also resulted in a changed flowering period, as, in 

 the north Oxalis cernna is in full blossom all the winter from November 

 to April, while it is described as flowering at the Cape in June and 

 July. The lengthening of the period is doubtless due, in part, to the 

 fact that no fruit being produced, the plant goes on flowering, as it 

 were, in hope, using up the energy which would otherwise be ex- 

 pended in the formation of fruit and seed. 



The Structure of Diatoms. 

 A RECENT number of the Verhandlungen des Naturhist. Med. Vereins 

 zu Heidelberg (vol. v., part ii.), contains an interesting paper on the 

 structure and nuclear division of Diatoms, by Dr. Lauterborn. 

 Readers of Natural Science (see Sept., 1892) will remember the 

 author's name in connection with some researches upon the move- 

 ment of these organisms which were carried on by him and Professor 

 Butschli. The present paper is a preliminary communication (with 

 one plate) of a more extensive work which Dr. Lauterborn promises 



