578 FILICALES 
one hand, and on the other to the Osmundaceae and certain of the 
early fossils. The general construction of the Hymenophyllaceous sorus 
is well known. Many satisfactory drawings are given by Presl, and 
other descriptive writers, which show how the 
sporangia with their oblique annulus are disposed 
with regularity of orientation upon the elongated 
receptacle, so that they overlap one another like 
the shields of a Roman ¢estudo. The orientation 
for each single sporangium corresponds essentially 
with that seen in Gletchenta or Loxsoma. This is 
well shown for TZvichomanes in the drawing of 
Goebel (Fig. 324). The sporangia are produced in 
basipetal succession upon the more or less elongated 
receptacle. This fact is demonstrated in Fig. 324 dvs, 
which represents the young sorus of Aymenophyllum 
Wilsoni already bearing the young sporangia (s) near 
the apex of the receptacle, while below there are clear 
indications of the active intercalary growth. The 
extent of the intercalary growth of the receptacle is 
greater in TZrichomanes than in Hymenophyllum, 
and the genera were by early writers distinguished 
on this ground, those with the receptacle exserted 
being ranked with the former, while those with it 
included fell into Aymenophyllum. Though this 
generic distinction will not hold accurately, still the 
general statement is correct that intercalary growth 
of the receptacle, and basipetal succession of the 
sporangia are longer continued in Zychomanes ; it 
is ghe extreme example of this mode of development 
of the sorus among Ferns, but none the less is it 
similar in kind to that described for other Gradatae. 
The sporangia in the Hymenophyllaceae differ 
Fic. 324. greatly in size, between a large, almost spherical 
Trichomanes tenerum. type, such as that of Hymenophyllum dilatatum (Fig. 
Sorus in surface-view; the 
ee ee 
distributed sporangia, ismes_ bodies such as are formed in many species of 
like indusium. The annulus Tyichomanes (Fig. 325, Nos. 99, 100, 101, 102); 
sporangia. Magnified. (After jt will be shown that with this goes a very wide 
difference in the output of spores. The large 
sporangia of ym. dilatatum are produced in relatively small numbers 
upon the short, but rather broad, receptacle; in size and form they are 
comparable to those of Gleichenta circinata (compare Fig. 325, No. 95, 
with Fig. 310 2 of Gi. circinata), while the annulus shows a similar degree 
of obliqueness. Externally there is close similarity, excepting in the dehis- 
cence, which is lateral in Aymenophyllum, a position which we shall see 
