filicineM. 467 



The nature of the sporangia of Psilotum and of Tmesipleris 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 tlie stern of J.ycoj>odiU7n Chamaxyparissiis (x iSo). 



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 oi Tmesipteris are, like those oi Psilotum, which they closely resemble in their development, 

 really distinct sporangia.] 



^ [For further details see De Bary's Vergleichende Anatomic, 1877.] 



H h 2 



