BUTTERWORT TRIBE 65 



pools. It has an erect stalk, from four to six inches in height, and in June 

 six or eight of the large bright yellow flowers grow from the upper part of 

 the stalk, and several inches above the surface of the pool. 



This plant is of great physiological interest, on account of the numerous 

 air-bladders which invest it. The shoots or runners are submerged in the 

 water, and are clothed at regular intervals with divided capillary leaves, 

 armed with distant minute spines. Attached to the leaves and shoots are 

 many little crested membranous bladders, of a green, purple, or pink colour. 

 The bladders are of a most curiovis structure. Each has an aperture closing 

 with an elastic valve, which Mr. Wilson has observed to be of a much thinner 

 texture than the vesicle to which it is attached. It opens inwards, and this 

 l)otanist i-enmrks that aquatic insects often enter the orifice, and are, of course, 

 confined there. All the species of Bladderwort have these little bladders on 

 some part of their structure, and by their aid entrap large numbers of the 

 small fresh-water crustaceans known as water-fleas, as well as the minute 

 larvae of water-beetles, etc. These are retained until drowned, and when their 

 bodies decompose, the enriched fluid is absorbed by certain glands for the 

 benefit of the plant. The French call the plant L' Utriculaire ; the Germans, 

 JFasserlauch ; and the Dutch, Neelekruide. In Denmark it is termed Fan- 

 drdllike, and in Norway VasswUike. It is sometimes called in country places 

 Hooded Milfoil. There is a rare sub-species, U. negleda, with more slender 

 stem, smaller leaves, the upper lip of the corolla exceeding the palate, and the 

 spur more conical. 



2. Intermediate Bladderv/ort {U. intermedia). — Spur conical ; upper 

 lip twice as long as the inflated palate ; leaves 3-parted ; segments linear and 

 forked ; perennial. This species is somewhat rare. It is altogether a smaller 

 plant than the last, and its pale yellow flowers have a much shorter spur and 

 a longer upper lip ; they are also fewer in number, and the flowering stalk is 

 not more than two or three inches high. The stems are more leafy, but the 

 bladders are placed on branched stalks, and not on the foliage. Their season 

 of bloom is July, but the plant seldom flowers, being mostly increased by 

 buds. Mr. Borrer has observed, however, that at this period the vesicles are 

 all immersed in the mud, and the leafy shoots float under water. The plant 

 is found in ditches and pits, and has been recorded from the counties of 

 Dorset, Hants, and Norfolk, and between Westmoreland and Sutherland, as 

 well as in Ireland. 



3. Lesser Bladderwort ( U. minor). — Spur very short, blunt ; upper 

 lip as long as the palate ; lower lip egg-shaped, flat ; leaves much cut into 

 forked segments, bladders upon the leaves ; perennial. This is a plant grow- 

 ing in ditches and deep pools throughout the country. It is a smaller but 

 rather stronger plant than either of the preceding, bearing from June to 

 September small pale yellow flowers, with scarcely any spiir. 



Utricularia hremii, a species resembling U. minor, but of more robust habit 

 and with more rounded lip, has been recorded from Moray and Nairn, in 

 Scotland, but as the specimens observed were not in flower, it is not im- 

 possible that a mistake may have been made. 



The Bladderworts can hardly be cultivated, but they grow wild in al)und- 

 ance in the pools and rivers of many countries, being often among the 



III.— 9 



