Morphology of Cycadean Sporangia . 437 
of its peripheral position. This view is only advanced as 
a possible way of explaining what must be regarded as an 
important difference between the sporangia of Marattiaceae 
and Cycadaceae. 
The similarity in the mode of dehiscence is a necessary 
result of the similar development of the epidermal layer. It 
is interesting on account of the close agreement between 
Stangeria and Angiopteris in all the essential features of the 
mechanism, and on this account is entitled to some weight. 
But, since there is no evidence to show whether the pre- 
sumable Fern-like ancestors of the Cycadaceae possessed 
separate or incompletely separated sporangia, it is equally 
possible that these resemblances afford rather a case of 
parallel development. 
The general conclusion so far as the results recorded above 
enable it to be stated is that Stangeria shows no characters in 
the development and structure of its sporangia which can be 
regarded as primitive in atiy further sense than is the case 
for other genera of the Cycadaceae. Some details, probably 
common to the other Cycads, appear to be shown more 
clearly in this genus. 
EXPLANATION OF FIGURES IN PLATE XXII. 
Illustrating Mr. W. H. Lang’s paper on Stangeria . 
Fig. 1. Under surface of the horizontal portion of a young sporophyll : a group 
of young sori is present on either side of the middle line. Slightly magnified. 
Fig. 2. Similar view of an older sporophyll. The earlier formed sori show 
separate sporangia : sori are still in course of development near the middle line 
and towards the margin of the sporophyll. Slightly magnified. 
Fig. 3. A group of sori from a sporophyll of the same age as Fig. 2, more 
highly magnified. To the right is a young sorus in which no indication of the 
sporangia is apparent. 
Fig. 4. Transverse section of a young sorus ; the sporangia are united in pairs. 
x — portion of sporogeno'us cells, x 80. 
Fig. 5. Part of a vertical (radial) section through a very young sorus, showing 
a single sporangium : c — the central point of the sorus ; x x — cells from which the 
sporogenous cells will be derived, x 400. 
