Anatomy of the Genus Selaginella , Spr. 
2 I 
12. Steinbrinck: Kohasions- oder ‘ hygroscopischer ’ Mechanismus. Ber. der deutsch. bot. Ges., 
xxi, 1903. 
13 . Harvey-Gibson : Contributions towards a knowledge of the anatomy of the genus Selaginella , 
Spr. I. The Stem. Ann. of Bot., viii, No. xxx, 1894. 
14 . - : Contributions towards a knowledge of the anatomy of the genus Selaginella, 
Spr. II. The Ligule. Ann. of Bot., x, No. xxxvii, 1896. 
The Anatomy of the Cone. 
General description. In the great majority of the species the fertile 
region is well marked off from the purely vegetative part as a definite 
strobilus, sometimes distinctly pedunculate (as in 5 . Helvetica ), frequently 
tapering towards the apex, and varying in dimensions according to the 
species. The length of the cones, which occur singly or in clusters at the 
tips of the branches (e. g. 5 . Kraussiana), ranges from one-quarter inch in 
the more delicate types (S. viridangida , S. haeniatodes , &c.) to the com¬ 
paratively massive structures of .S'. Helvetica and .S. spinosa , which often 
attain a length of two or even three inches. The leaves are generally 
smaller and less expanded than they are on the vegetative region of 
the stem, being more in the nature of protective bracts (though the reverse 
is true of S. Helvetica , S. spinosa , &c., where the axes have small isophyllous 
leaves, and the sporangia are extremely large), and are hollowed to 
accommodate the sporangia, which arise one in the axil of each leaf. In 
some cases, notably 5 . Lyallii and 5 . rupcstris , the leaves have a strongly 
recurved portion at the junction of the leaf-base and the upturned lamina, 
so that the sporangia come to be enclosed in a definite chamber—an obvious 
adaptation to the environment. Homophylly is not a constant feature 
of the cone ; .S'. molliceps , for example, has a resupinate arrangement of 
leaves. The degree of compactness and regularity of outline are determined 
by the set of the leaves. The sporophylls are, in all cases, spirally arranged 
round the axis (as can easily be seen in the straggling cones of .S'. Helvetica :), 
but the spiral may become so condensed that the leaves arise almost opposite 
to each other, in four distinct rows, the lower ones considerably overlapping 
those immediately above. Beyond the somewhat narrowed leaf-base the 
lamina curves sharply upwards, parallel with the axis of the cone, thus giving 
the regular quadrangular outline so characteristic of 5 . Wildenowii, S. Wal- 
licHii , &c. As a general rule the cone is terminal and unbranched. The 
following interesting variations from the normal type may be referred to :— 
a. S. patula and S. cuspidata (cf. PL IV, Fig. 14) :— 
Beyond the fertile homophyllous cone, the axis continues to grow 
vegetatively, reverting to the dorsiventral structure characteristic of the 
ordinary stem. 
b. An unnamed species from India, probably .S', pennata , exhibited the 
same phenomenon, save that abortive sporangia were produced in the axils 
