467 
The nature of ihe sporangia of Psilotum and of Tmesipteris is in many respects 
obscure. In Psilotum the short branches which bear the apparently trilocular 
sporangia^ arise as lateral papillae on the growing point, and, according to Juranyi, 
are provided with a three-sided apical cell like the vegetative branches. A fibro- 
vascular bundle runs from that of the parent shoot to the papilla, but does not 
extend beyond the half of its height. The two small leaves of this fertile branch, 
which were formerly regarded as being the segments of a single leaf, arise separately 
from the papilla and coalesce at a later period. Even at a tolerably advanced stage 
the papilla still consists of undifferentiated tissue which, as in the case of the anthers 
of Phanerogams, forms parietal layers and three groups of spore-mother-cells ; in 
this way three loculi are formed, which are separated by longitudinal walls and an 
axial mass of tissue, and which project considerably on the exterior. I regard these 
three loculi as so many sporangia which are formed in the apical part of the fertile 
shoot to which the axial fibro-vascular bundle extends. In Tmesipteris the spo- 
rangium, which is apparently divided into two loculi by a transverse septum, is borne 
upon a small lateral branch which bears a leaf to the right and to the left. 
Fig. 328. — Transverse section of the stem of Lycopodinm Ckajncscypan'ssns (X 150). 
Histology'^. The Epidermis of the leaves of L. annotinum, cla'vatum^ and Selago, 
is provided with stomata on both surfaces; the stomata are often arranged in small 
groups. The leaves of the heterophyllous species which have them arranged in four 
rows, possess stomata on their inner surface ; stomata occur on the outer surfaces 
of those portions of the leaves which adhere to the stem and which are directed 
towards the earth. The epidermis of the root is sometimes strongly cuticularised, as 
in L. cla-vatum. 
The Fundamental Tissue of the stem consists of cells which are sometimes thin-walled 
throughout, as in L. inundatum, but usually the inner layers have thick walls, and are 
^ [This has been cleared up by Goebel (Beitr, z. vergl. Entwick. der Sporangien, Bot. Zeit. 
1881). He finds that the 'trilocular sporangium' oi Psilotum is really a group of three sporangia, 
each, of which contains primarily a unicellular archesporium, from which a two-layered tapetum is 
subsequently derived, as also the mother-cells of the spores. The ' loculi ' of the apparently bilocular 
sporangia of Trnesipteris are, like those of Psilotum, which they closely resemble in their development, 
really distinct sporangia.] 
^ [For further details see De Bary's Vergleichende Anatomie, 1877.] 
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