i5 
Phylogeny of the Cyperaceae. 
zone. The figure of Eleocharis (Fig. \%) represents another type of 
this class, in which the medullary tissue is still further reduced, and 
the assimilatory zone is quite undifferentiated. 
We may now examine the culm of Scirpus cyperinus as a fair type 
of the Sclerocyperaceae, though it is by no means an extreme example 
of the sclerotic habit. As shown in Fig. 5, the bundles of the internode 
are fairly numerous, collateral, and with centripetally massed peridesm. 
The bundles of the outermost series alternate with rather large irregular 
air-spaces. It should be observed in passing that these air-spaces differ 
from those occurring in the medulla of the Chlorocyperaceae in that 
they are lysigenous, or rhexigenous, according to De Bary ( 12 ). The 
medulla consists of thin-walled parenchyma, which in this species shows 
a tendency to break down in mature stems. The epidermis is covered 
by a thin, smooth cuticle. In species which show conspicuous hypodermal 
ribs, as in A. robustus , the epidermal cells are very much smaller over 
these ribs than elsewhere. In .S', cyperinus the epidermis shows no stomata, 
and is subtended by a continuous zone of sclerenchyma which in very 
many cases is produced into strong ribs which connect internally with 
the peridesm of the interlacunar bundles. The more general anatomical 
features of the aerial stems of the Cyperaceae studied in the present 
investigation are briefly set forth in Table II. 
TABLE II. Aerial Stem Characters. (Explanation.) 
The symbols 4- and — are used here with the same variation’s in significance 
as already indicated in Table I. 
1. Class: S, Sclerocyperaceae; or C, Chlorocyperaceae. 
2. Form: t, triangular; q, quadrangular; r, round; s, scapose ; or j, jointed. 
3. Medulla : a, aerenchymatous ; c, compact ; s, sclerotic ; or 0, a large lacuna. 
4. Cortical Air-spaces: +, numerous; — , few; or 0, none. 
5. Cauline Bundles : s, scattered, few ; or c, crowded, many. 
6. Peridesm : = , uniform ; c, centripetal ; 0, undifferentiated ; or x, joined in 
a continuous mechanical zone. 
7. Cortical Bundles: +, many; — , few; or 0, none. 
8. Hypodermal Sheath: +, strongly developed; — , slightly developed; or 
0, wanting. 
9. Hypodermal Ribs: +, numerous; — , small or few; or 0, none. 
10. Palisade and Stomata: +, well developed; — , poorly developed; or 
0, absent. 
11. Tannin-sacs : +, many; — , few; or 0, none. 
12. Bundles of Leaf-trace : average number, where observed. 
