Identifier: structuredevelop00camp3 Title: The structure and development of mosses and ferns (Archegoniatae) Year: 1918 (1910s) Authors: Campbell, Douglas Houghton, 1859-1953 Subjects: Publisher: New York, Macmillan Contributing Library: The LuEsther T Mertz Library, the New York Botanical Garden Digitizing Sponsor: The LuEsther T Mertz Library, the New York Botanical Garden

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Text Appearing Before Image: are more extendedlaterally than the othercells of the annulus, andbetween them the spo-rangium opens by a widehorizontal cleft Atkinson ((3), p. 68)describes the processo| thus for the Polypodi-aceae. While the open-ing of the stomium be-tween the lip cells is aid-ed by their peculiar form,it seems possible that atmaturity the line of un-ion is less firm than be-tween the other cells.The fissure once startedproceeds across the lat-eral walls of the sporan-g i u m , usually in astraight line, thus split-ting in half the cells of the middle row, their frailty favouringthis. The drying of the annulus brings about the unequal ten-sion of its cell walls. During this process it slowly straight-ens, carrying between the distal portion of the lateral wallsof the sporangium, which remain attached to the free extrem-ity, the greater part of the spores. When straight, it continuesto evert, and this usually proceeds until the two ends of theannulus nearly or quite meet, when with a sudden snap it

Text Appearing After Image: Fig. 191.—Surface view of a nearly ripe sporan-gium of Polypodium falcatum, Xi75; st,stomium; r, annulus. IX FILICINEJE LEPTOSPORANGIATAl 345 throws the spores violently away and returns to nearly itsnormal position. Paraphyses, in the form of pointed hairs, often with aglandular terminal cell, sometimes occur with the sporangia.These in some Ferns, e. g., Aspidiuin filiv-mas, are directoutgrowths of the sporangium itself. CHAPTER X THE HOMOSPOROUS LEPTOSPORANGIAT^ (FILICES) Fam. I. OsMUNDACE^ (Diels (/)) The Osmundacese, which in many respects form a transitionfrom the eusporangiate to the leptosporangiate Fihcineae, arerepresented by two genera, Todea (inc. Leptopteris), with fourspecies, mostly confined to Australasia, one species onlybeing found in South Africa; Osmunda, with six or sevenspecies, belonging mainly to the temperate and warm temper-ate regions of the northern hemisphere. The widely distrib-uted species 0. regalis is found also in South Africa, but other-wise they b

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