EE VISION or THE GENUS NAJAS. 425 



death of the older connecting parts Length of shoots varying from a few inches to over 

 2 feet. Lateral branches sometimes very short, forming a densely-leaved tassel, and, when 

 the internodes on the main stem are also short, giving the plant a dense cylindrical habit. 

 Internodes terete, sometimes broadening upward on tlie stronger shoots, the lowest 

 generally from 2 to 45 cm. long by 1 to 1-75 mm. wide, becoming smaller and often 

 fairly regular in size about the middle, and then decreasing to the apex, where the leaves 

 are densely crowded ; in the spreading forms the internodes often reach 8 cm. in length 

 by 1 mm. in diameter. The densely-leaved lateral shoots and tips of the main shoots 

 with narrow linear spreading recurved leaves often give a very graceful plumose habit. 

 to the plant ; in the laxer specimens the leaves are generally longer, weaker, and less 

 recurved. 



A more delicate plant, bright green in colour, with almost filiform internodes (about 

 1"5 cm. long by "5 mm. diameter in the middle of the shoot) and small, narrow, weak, 

 recurving leaves, comes from Gwalior, Northern India, 



The long thread-like roots are reddish-brown in the plants which have become 

 established near Manchester. 



Leaves from 15 to 2*5 cm. long by 4 to 6 mm. in width. Sheaths from 2'5 to 325 

 cm. long, including the auricle (1 to 1*75 mm.) ; the latter bears a few rather small teeth 

 on both inner and outer edge, about 10 altogether. Intravaginal scales '75 to 1 mm. 

 long. Marginal teeth 30 to 50 in number, consisting of a sharp ascending spine supported 

 by two generally but slightly projecting epidermal cells. 



Below the epidermis runs a single row of long, narrow, colourless, supporting cells 

 ("libriform cells ") ; these are absent in some Egyptian and Syrian specimens and in the 

 plants found near Manchester, w^hich Magnus has separated as the variety Delilei. 

 As, however, these specimens can be distinguished by no other character, their habit, 

 leaf-sheaths, marginal teeth, flowers, fruits, and seeds conforming to those of the type, 

 which moreover grows in the same area, I have ventured to disregard the variety, 



Floivers borne on the short lateral shoots, often several at the same node. From the 

 dried material at command it is impossible to make general statements as to their 

 relations, but in fresh specimens from the locality near Manchester no flowers were 

 found in the axils of the two lowest pairs of leaves of the fertile shoot, the fertile (lower) 

 leaf of the next higher pair sheathed a reduced shoot with several (4) female flowers, 

 and that of each succeeding pair a reduced shoot consisting of a male and female flower 

 standing side by side. 



Male flowers before dehiscence of anther about 1 mm. long; perianth ending directly 

 above the anther in two rounded ear-like lobes, which may be somewhat oblique ; in the 

 living specimens from Manchester they were tinged at the edge with red ; anther oblong 

 or oval-oblong. The flower-stalk elongates before dehiscence, becoming almost as long as 

 the anther ; the apical lobes of the perianth separate to allow the pollen to escape. 

 Pollen dimorphic, grains larger and obloug and smaller and roundish, the latter with 

 denser contents. Female flowers 1*3 to 1(5 mm. long. Fruits solitary or 2 to 4 

 crowded together at the base of the dwarf shoots ; narrowly oblong or narrowly 

 ellipsoidal or ellij)Soidal- oblong, tapering more at the tip, in the fresh specimens greenish- 



