1914I S NOW— DIAPHRAGMS OF WATER PLANTS 513 



ragms have been found in immersed and in. aerial 



parts of plants. 



4. Diaphragms appear to be 

 in water or very wet places. 



5 



ragms varies : (a) they may 



several layers thick; (b) the cells vary from polygonal to stellate; 

 in the "scirpus type" the cells are in groups (usually of four) and 

 are long and narrow, with short arms; (c) the presence of cross- 

 bundles appears to vary with the form studied. In Scirpus 

 validus nearly all the diaphragms have bundles in them. 



6. The cross-bundle is made up of xylem and phloem. At 

 first the connection with the longitudinal bundles is with the 

 phloem, but later a secondary connection is made with the xylem. 



7. The stellate cells originate from ordinary parenchyma cells 

 by the differential growth of the cells from the inside outward. 



8. Diaphragms in Scirpus validus arise by a division of the 

 parenchyma into layers, some of which retain their meristematic 



remamin 



become the slender 



diaphragm of Scirp 



mo 



formation 



determined 



materials Dassine from 



walls of the space. 



10. Diaphragms have the following functions: (a) to resist 

 strains and keep the spaces open; (b) to support cross-bundles; 

 {c) to prevent entrance of water by the small size of the perforation; 

 (d) perforations permit air to circulate; (e) while young and green, 

 to manufacture carbohydrates; (/) to store food: (i) this is possibly 



form of some tannin compound containing the phlorogi 



radical, and may or may 



this 



hich are distinct from 



starch-bearing cells; (g) to conduct food materials from 

 bundle to the partition walls of the space. 



My thanks are due Professor Karl M. Wiegaxd for his 

 kindly assistance in the identification of the species studied, and 



