VEGETATIVE REPRODUCTION IN SAGINA NODOSA 271 



tensive development of aquatic mosses in the moister portions of 

 the slacks, it tends to become more restricted to the sloping 

 margins at the foot of the dunes, where an interesting bryophytic 

 plant-association occurs. 



It will be recalled that in »S. nodosa the main stem remains 

 short, and bears numerous, comparatively long, subulate leaves, 

 from the axils of which lateral flowering-stems are given off. In 

 the leaf-axils of these lateral stems are developed fascicles of small 

 leaves, which in due time drop off, and easily strike root if the 

 conditions are favourable. These bulbils in my specimens measur- 

 ed 1-2 mm. long, and had three or four decussate pairs of short, 

 plump, semi-terete leaves, generally tinged with purple. The 

 parenchyma of these leaves consists of a dense mass of very 

 chlorophyllose cells, full of reserve food material. 



The first sign of the root is the appearance of a minute whitish 

 protuberance immediately at or a little to one side of the extreme 

 base of the lowest pair of leaves. The root rapidly grows and 

 develops root-hairs. This primary root is soon followed in many 

 cases by a second, also from the base of the lowest leaves, and, 

 more rarely, by a third. Usually, only a single tap-root is de- 

 veloped. From the rapid deterioration of the lowest pair of 

 bulbil leaves, it is evident that nearly the whole of the food 

 material they contain goes to the development of the root system. 

 In cases where the root had only attained a length of 2 mm., the 

 lowest pair of leaves had already become yellow, thin, and flaccid. 

 Subsequently to the appearance of the primary root or roots, one 

 or two adventitious roots are frequently given off from the axils 

 of the lowest leaves of the bulbil, and often attain nearly the same 

 size as the main root. During the development of this root system 

 the upper leaves of the bulbil doubtless function to some extent 

 as true leaves. The leaves of the second pair lengthen and become 

 less plump, and in the third pair this is particularly noticeable. 

 During this development a slight lengthening of the internodes of 

 the bulbil takes place. Above the uppermost pair of bulbil leaves, 

 however, a very marked elongation of the main axis commences, 

 the axis growing very considerably and carrying up the new leaves 

 quite clear of the bulbil. In specimens which I strewed on moist 

 dune- sand and kept under a hand-glass, the tap-roots appeared, in 

 most cases, in a few days' time and grew rapidly, but, after that 

 period of activity, development seemed to lag, and in a month's 

 time (towards the end of December) typical specimens were only 

 5 mm. long (exclusive of roots), and bore a pair of young leaves 

 still folded face to face. 



In fresh material collected in the second week of January, it 

 was found that the great majority of the bulbils had taken root, 

 and in many cases they were as far advanced as those I had in 

 cultivation. By the strong development of the tap-root the bulbil 

 is eventually pulled down into the ground, and in plants sufliciently 

 developed to show two or three pairs of young leaves the bulbils 

 were below the surface of the soil, and the first and second pairs 

 of l)ulbil leaves had almost decayed away. 



