2 



A. B. Rendle. — Najadaceae. 



Vegetative Organs (Vegetationsorgane). The plants vary from a few centimetres 



to 6 dm in height and show considerable Variation in habit depending on the direction of 

 the branches and the length and thickness of the internodes. The stem branches shortly 

 above the base. The branches may be long and spreading or ascend from a decumbent 

 base with a grass like growth, or may form a much-branched System in which each lateral 

 axis grows as strongly as the main axis and gives rise to a dense apparently dichotomous 



Fig. I. A— C, Najas marina L. A Habitus. B Flos Q. C Fl. <3 longit. sectus. O Fl. $, 



spatha perianthioque divulso. — D—F N. minor All. D Habitus. E Fl. Q, F Fl. $ longit. 



sect. — H N. flcxilis Rostkov. et Schm. Fl. Q. (See. Magnus; e spatha, i perianthium). 



growth (-e. g. in N. minor). Frequently the elongated shoots end in a dense dichotomous 

 growth. 



The sueculent internodes are often very brittle, as in the common species JV. marina 7 

 they are generally unarmed but in some forms of N. marina are furnished with short 

 spine-bearing teeth. 



The leaves are apparently opposite; each pair however consists of an upper leaf 

 which arises at a slightly higher level at the growing point and a lower one. Each pair 

 forms an acute angle with preceding and sueeeeding pairs. A branch arises in the axil 

 of the lower leaf only, starting from the second pair above the cotyledon. The lowest 

 leaf on the branch is reduced to a small scale subtending a leaf-bud. The lowest deve- 

 loped leaf of the branch, namely the upper leaf of the lowest pair, in which no bud 

 arises, forms together with the adjacent pair of leaves on the main axis an apparent whorl 

 of three. 



The sheath is well-developed and sharply distinguished from the lamina. The edges 

 of the sheath of the lower leaf overlap the sheath of the upper leaf which is itself amplexi- 

 caul. The sheath may be truncate or have more or less sloping Shoulders, or the Shoulders 

 may be drawn out into longer or shorter auricles. The upper margins and auricles are 





