GoebeL — On the Simplest Form of Moss. 359 
possible of conducting tissue ; the same relation is shown by 
the pollen-sacs of many Phanerogams 1 . If now, as Bower 
contends, the sporophyll of Ophioglossum is homologous with 
a sporangium of Lycopodium , and has come to be what it is 
by s elaboration, partial sterilisation, and consequent partition- 
ing of the sporangium,’ this must be true of other sporophylls 
as well. But even the sporophylls of Botrychiuni are clearly 
modified leaves, and this is especially obvious in cases where 
a few sporangia are developed on usually sterile leaves ; the 
greater the number of the sporangia, the more does the leaf 
become modified and take on the characters of a sporophyll, 
as is shown by figures which I have published 2 . In fact, the 
whole sterile portion of the leaf may be modified into a spo- 
rophyll. I reproduce in Plate XXII, Figs. 1 and 2, two 
pinnae which show partial modification ; it is easy to see how 
the appearance of sporangia leads to the segmentation of the 
leaf into separate lobes, the sporangiophores. 
Moreover, it can be experimentally proved that the sporo- 
phylls of the Leptosporangiate Ferns are modified leaves, as 
I showed some years ago in the case of Onoclea Struthiopteris 3 . 
As is well known, the sporophylls of this Fern are widely 
different from its foliage-leaves ; they contain but little 
chlorophyll, they are erect, and their pinnae are simple and 
have their margins incurved for the protection of the sporangia. 
I succeeded, by a simple method, in converting young sporo- 
phylls, either partially or completely, into foliage-leaves, and 
I now give some illustrative figures which may be of interest. 
In Fig. 3 of Plate XXII is shown a form of leaf intermediate 
between a sporophyll and a foliage-leaf ; the lowest pinnae are 
still circinately infolded, the upper ones are expanded and 
have assumed the characters of ordinary foliage-leaves. Figs. 
4 and 5 represent pinnae, more highly magnified, in which the 
characters of the foliage-leaf in the upper -part are combined 
1 Goebel, Entwicklungsgeschichte der Pflanzenorgane, Schenk’s Handbuch der 
Botanik, III. p. 398, Fig. no, 1883. 
2 See Schenk’s Handbuch d. Bot, III. p. hi, Fig. 1. 
3 Ueb. kiinstliche Vergriinung der Sporophylle von Onoclea Struthiopteris , 
Hoffm., Ber. d. deutsch. bot. Ges., 1887, p lxix. 
