NATURAL HISTORY OF BHOMPSTON POND. 229 



BOTANY. 



If we now turn our attention to plant life, we find Ranun- 

 culus aquatilis (water crowfoot), with its small white flowers and 

 leaves deeply cut into slender filaments, a form of leaf often 

 found in aquatic plants. The closely allied R. ftammula 

 (Lesser Spearwort) and the curious little Hydrocotyle vulgaris 

 (Marsh Pennywort) grow in the shallower water. A transverse 

 section of the petiole of the latter shows three vascular bundles 

 (one of which is shown in fig. 99) surrounded by cortex 

 (a) and epidermis. The xylem vessels (b) are grouped in four 

 sets surrounded by xylem parenchyma (c) and are partly 

 encircled by the phloem (d). 



Myosotis palustris (Forget-me-not) is common on the 

 western side of the pond, but still more so is Menyanthes 

 trifoliata (Marsh Trefoil). On this side of the pond are 

 Epilobium hirsutum (Great Willow Herb) and E. parviflorum 

 (Small-flowered Hairy Willow Herb) ; a transverse section 

 of the root of the latter shows the endogenous origin of the 

 lateral roots. The vascular bundles can be seen to have 

 fused together, forming a ring enclosing the pith. By the 

 activity of the phellogen in the pericycle the cortex and 

 epidermis is already almost cut off from the stele by a ring of 

 phellem. 



Here, as in most ponds, Lemna minor (Lesser Duckweed) 

 is extremely plentiful, and supplies an example of a root- 

 pocket, which functions as a calyptra (root-cap). Spread 

 over the surface of the southern part of the pond is 

 Potamogeton natans (Floating Pond -weed), with smooth 

 elliptical leaves and spike inflorescences. Clusters of 

 Alisma Plantago-aquatica (Great Water-Plantain) occur 

 amongst the Pond- weed, the delicate white flowers of 

 which are arranged in a panicle some three feet above the 

 water. 



The well known brown spikes of pistallate flowers of Tijpha 

 latifolia (Great Reed-Mace) are to be found on the eastern side 

 of the pond. The slender extremity of the spike consists of 



