CONTRIBUTIONS TO THE KNOWLEDGE OF THE 



DIAPHRAGMS OF WATER PLANTS 



I. SCIRPUS VALIDUS 



Laetitia M. Snow 



* 



(with sixteen figures) 



I. Introduction 



The form and structure of water plants have been studied by- 

 botanists for many years and much has been written on the subject. 

 Many of these investigators, however, have not mentioned the 

 presence or absence of diaphragms in the plants which they have 

 studied, and the reports of those who have considered these struc- 

 tures are often contradictory. The aim of the present paper is to 

 organize these numerous and conflicting reports and to present 

 certain results, which have been obtained chiefly from a study 

 of Scirpus validus Vahl. The other forms which have been studied 

 will be referred to as occasion demands. The work has been 

 carried on at Wellesley College and Wood's Hole. 



II. Definition of the term "diaphragm" 



Leitgeb (18) evidently considers a diaphragm as any partition 

 which breaks the continuity of the air passage, for he speaks of 

 them as being present at the nodes of Hippuris. Duval- Jouve 

 (7), DeBary (6), and Schenck (29) deny the presence of dia- 

 phragms in Hippuris, but Goebel (13) uses this form as an example 

 of a water plant with diaphragms. Meyen (20) states that the 

 hollow stems of the umbellifers and grasses have no cross-walls, 

 but are interrupted at the nodes by masses of tissue. Courchet 

 (4), however, considers that diaphragms are present at the nodes of 

 the umbellifers, and Hackel (11c) mentions diaphragms of thick 

 tissue at the nodes of grasses. Meyen (20, 21) states that the 

 canals in the leaves of Ceratophyilum and in the stem of Myrio- 

 phylliim spicatum end blindly in thick tissue. According to Duval- 

 Jouve (7) no diaphragms are found in Myriophyllum verticillatum , 



495] 



[Botanical Gazette, vol. 58 



