330 DR. E. DE FRAINE ON THE 
which has resulted entirely on account of the physiological needs of the 
plant. The genus Salicornia is composed entirely of. pronounced halophytes, 
leaf reduction may have occurred in response to the environmental require- 
ments of the plant, then, to provide the necessary assimilation surface the 
broad bases of the sessile leaves fused and became decurrent down the stem, 
thus giving rise to the curious jointed shoot of the group. 
SPIRAL CELLS AND STEREIDES, 
A very characteristic feature in the anatomy of many species of Salicornia 
is the occurrence of spiral, or spicular cells, or both. 
The spiral cells are large, sac-like, colourless elements which occur wedged 
in between the palisade cells of the assimilating layer of the foliar organs, 
their long axis parallel with the palisade cells (РІ. 15. fig. 8). The cell wall 
of these elements is thin and is composed of cellulose, though in a very few 
cases in 9, fruticosa, Linn., a slight trace of lignifieation has been observed. 
A closely wound spiral thread of cellulose lines the inner wall and r iches 
nearly to the rounded ends of the elements. The length of the spiral cells 
is very variable ; in the lower parts of the segments they are short and arely 
extend much beyond the palisade layer, but in the upper region of each 
segment, in the free leaf-tips, and especially in. the flowering spike. they are 
frequently extremely long. The epidermis is rarely reached by the spiral 
cells, and the relation between them and the stomata does not appear to be a 
definite опе. In this connection, however, Duval-Jouve * states that “elles 
sont constamment situées ou directement au-dessous ou tout à cóté d'un 
stomate, mais non en contact." This position does occasionally occur, but it 
is by no means a constant characteristic of any of the species we have 
examined. Mangin f, likewise, does not agree with Duval-Jouve’s observa- 
tion, for he found that spiral cells were often separated from the epidermis 
by a parenchymatous cell. He further noted the occurrence of protoplasm 
and a nucleus in many of them, and traced their development from elements 
of the chlorenchyma. Spiral cells are never directly connected with the 
vascular bundle system. 
The distribution of the spiral cells in the various parts of the plant seems 
to be similar in all the species in which they occur. The basal region of the 
segment is always destitute of them, in the middle region they begin to 
appear, and increase in number until the free leaf-sheath is r 'ached, in which 
position they are most abundant. In the reproductive shoots the spiral cells 
attain their maximum development, both as regards size and number. They 
are found in the flowering spikes of such species as S. prostrata, S. herbacea, 
* Bull. Soc. Bot. France, xv. (1868) p. 184. 
+ Mangin, L. : “Sur le développement des cellules spiralées.” Bull. Soc. Bot. France, 
xxix, (1882) p. 16. 
