PROF. F. О. BOWER ON APOSPORY AND ALLIED PHENOMENA. 825 
Fig. 3. An arrested sporangium with annulus already formed, but its cell-walls not thickened ; the cells 
of the head of the sporangium have almost lost their contents, while those of the stalk (st) 
have abundant protoplasm and chlorophyll granules. ( х 325.) 
Fig. 4. A sporangium taken from a sorus after cultivation on moist soil, at high temperature, for seven 
days. The shaded head of the sporangium has not grown, but active cell-division and growth 
have gone on in the stalk (sé). (х 825.) 
Fig. 5. Sporangium after germination at normal temperature for three months: the head (Л) has not 
grown ; irregular outgrowths from the stalk (s/) immediately below it. (х 175.) 
Fig. 6. An arrested sporangium in which the archespore (a) remains undivided; the stalk (st) is 
abnormally enlarged, and its cells as well as the superficial cells of the head have abundant 
protoplasm and chlorophyll. (х 325.) 
Fig. 7, A similar sporangium, as seen in optical section after culture at normal temperature for three 
months. (х 175.) 
Fig. 8. Superficial view of a similar sporangium, with enlarged head. (х 825.) 
Fig. 9. Ditto, head not enlarged, but whole sporangium elongated. (х 175.) 
Fig. 10. Sporangium, after culture for three months, developed as a solid cylindrical mass. gl= 
glandular hair, st=stalk. ( x 175.) 
Fig. 11. Ditto, ditto, an antheridium (anth) already showing characteristic structure. (x 175.) 
Fig. 12. A sporangium after seven days’ cultivation at high temperature, showing a flattened irregular 
outgrowth from the stalk. ( x 325.) 
Fig. 13. Ditto, after twelve days, growth with a wedge-shaped apical cell has begun laterally on the 
enlarged stalk. (х 130.) 4 
Prate LVIII. 
Athyrium Filix-fæmina, var. clarissima (continued). 
Fig. 14. A flattened expansion produced by cultivation of an arrested sporangium ; growth witha wedge- 
shaped apical cell appears to be progressing at more than one point. (x 130.) 
Fig. 15. Part of a pinnule, with vascular bundles (v.d.) and опе sorus. Cultivation, at a high tempe- 
rature, for five weeks has resulted in the development of prothalli from some of the arrested 
sporangia; these prothalli bear antheridia and archegonia, but are still attached to the pinnule 
which bore them. (x 40.) 
Fig. 16. Single prothallus from a similar culture, showing antheridia. s¢=stalk of sporangium, an= 
antheridia, r=root-hairs. (х 65.) 
Polystichum angulare, var. pulcherrimum. 
Fig. 17. Tip of a normal pinnule as seen in surface view. ( х 130.) 
Fig. 18. Tip of a pinnule which has begun to assume а prothalloid character with thin cell-walls: as yet 
there is no distinct apical cell. (x 130.) 
Fig. 19. A similar growth more advanced. (х 20.) | 
Fig. 20. Apex of the same under higher power, there is no apical cell, no cushion, nor sexual organs, 
( x 130.) 
Flattened expansion from apex of pinnule has attained considerable size, and typical characters 
of prothallus, with glandular hairs (g/), cushion (c), and sexual organs, which proved, on 
cutting sections of the prothallus, to be antheridia and archegonia. ( x 20.) 
Tip of pinnule, showing a prothalloid growth (prth) beginning on the surface above the 
ending of the nerve (vb). (х 20.) 
Section through such a prothalloid growth (prth), the end of the nerve (vb), and the apex of 
the pinnule (ар). ( 179.) 
SECOND SERIES.— BOTANY, VOL. II. 
Fig. 21. 
Fig. 22. 
Fig. 23. 
зе 
