The President's Address. By Lord Avebury. 151 



A. maculatum is widely distributed in Britain, and on the 

 Continent extends from Gothland to North Africa. On the other 

 hand, A. italicum is found only in six southern counties, and on 

 the Continent extends from Holland to North Africa. It would, 

 therefore, seem to be less hardy and to require a higher temperature 

 for its well-being. It has larger fruits and seeds than its relative, 

 and the leaves are sometimes variegated with yellow veins. The 

 leaves are produced in winter, and that alone would tend to restrict 

 its distribution northwards. 



Acorns (the Sweet Flag). — The spike contains many hundred 

 flowers. It never, however, produces ripe fruit in Europe, though 

 it does in Asia. It is probable that this is clue to the absence 

 of the proper insects for fertilisation. Ludwig suggests that all 

 our European plants are descended from a specimen brought from 

 the East by Clusius. Bentham, however, regards it as native in 

 some of our eastern counties. 



Lemnace.e. — This small family of minute floating or submerged 

 plants consists of two genera and about a dozen species. Both 

 genera and five species are British. 



The fruit is a sub-fleshy utricle, indehiscent or dehiscing cir- 

 cumcisely. It contains one to seven erect seeds, which may be 

 either auatropous or orthotropous. The endosperm is fleshy, but 

 sometimes may almost be said to be wanting. 



The plants increase principally by budding from the margins 

 of the fronds, and in autumn by bulbils. The flowers are rare, 

 in fact, L. polyrrhiza, the largest species, though native in fifty-six 

 botanical districts, has never been known to flower in Britain. 



Wolffia arrhiza, again, has never been known to flower in 

 Britain, or indeed, in Europe ; the descriptions given are taken 

 from African specimens. 



No doubt the plants are disseminated by birds, and of course by 

 currents and floods. 



Alismace.e. — The Alismacese are marsh or water plants. In 

 Britain we have six, or perhaps seven genera, some of which are 

 represented by more than three species, but most by only one. The 

 ovary consists of three, six, or many carpels. The fruits differ con- 

 siderably in form and character. Those of Alisma are small 

 achenes. Those of Sagittaria are flattened and winged. The fruit 

 of Damasonium is a 2-seeded follicle, six of which are usually 

 arranged horizontally in the form of a star. The carpels of Butomus 

 (the Flowering Rush) are also beaked, but erect. The seeds are 

 campylotropous, those of Damasonium being most completely 

 folded. In Butomus they are small, very numerous, anatropous, and 

 scattered all over the inner face of the follicles. The seeds contain 

 a homogeneous mass, generally regarded as being an embryo with- 

 out albumen. The achenes of Sagittaria are flattened and winged. 

 The seeds are shining and not wetted by water, so that they float 



