ILLUSTRATIONS. 115 



lobed lower lip ; two stamens ; and a one-celled ovary opening 

 in two valves and containing many seeds. The common name 

 of Butterwort appears to have arisen from the property which 

 the leaves are said to possess, of coagulating milk. 



The peculiar features of the Monochlamydeous group have 

 been already pointed out. During the summer period many 

 flowers having this peculiar structure will be met with, but the 

 limited number of our figures will, as before, only afford a few 

 selected illustrative examples. 



We have here, first, the Bistort or Snakeweed,"'^ a sample of 

 the Polygonaceous family, which is distinguished among Mo- 

 nochlamyds by having sheathing stipules. The Bistort is a 

 perennial herb, found growing in moist pastures in various 

 parts of Britain. It has a thick rootstock, from which spring 

 up the patches of long-stalked ovate or cordate leaves, which 

 are remarkable for their sudden contraction at the base into a 

 narrow wing which borders the stalk. These are the leaves 

 springing from the base of the plant, and are called the radical 

 or root-leaves. The flower-stem grows quite upright, one to 

 two feet high, with a few leaves on the lower part similar to 

 the others, but smaller and with little or no stalk ; at their 

 base however is a kind of sheath surrounding the stem, so that 

 the latter appears to grow through it. The sheath is formed 

 of the united stipules — stipules being a pair of appendages 

 assuming a variety of forms, produced on either side of the 

 petiole or leaf- stalk at its base in certain families of plants. 

 Here they coalesce and form a sheath or tube. The flowers 

 form a close oblong spike at the top of the stem, and are of a 

 pretty pink or light rose colour. The flowers have but one 

 floral envelope, which is called the perianth, and this consists 

 of five nearly equal segments, eight stamens considerably 



* Polygonum Bistorta — Plate 19 A. 



I 2 



