1893.] Morphology of Spore-producing Members. 175 



synangium is a growth from its upper surface. This latter view I 

 am able to support from evidence of sections both of Psilotum and 

 Tmesipteris. The latter shows the synangium to originate below the 

 apex of the sporangiophore, and from its upper surface, in a manner 

 very similar to the sporangium of Isoetes. The form of the young 

 synangium resembles that of the sporangium of Lepidodendron, with 

 which genus also there is extraordinary anatomical similarity. The 

 position so close to the apex of the sporangiophore is peculiar, but it 

 is to be noted that there is variety among other Lycopodinese in the 

 position of the sporangium. The septum is similar in its origin to 

 the sporogenous masses, and is not at first distinguishable from 

 them ; in this respect it also resembles Isoetes. It would thus appear 

 that the whole synangium is comparable in origin and position, in the 

 broad lines of development, and in function to the sporangia of other 

 Lycopods, that is, a septate comparable with a non-septate body. 



Misgivings which may be felt in face of such a conclusion will be 

 in great measure removed by the results of study of certain modifica- 

 tions to which the synangia are liable. Tmesipteris appears to be a 

 variable plant as regards the form and structure of its synangia ; 

 there is, however, some method in its irregularities ; smaller synangia 

 of simpler form and structure are found at the limits of its fertile 

 zones, while about the middle of it synangia have been found with three 

 loculi, corresponding to those of Psilotum. Examination of those of 

 simpler form shows that they may be only partially septate, or the 

 septum may be absent from the first. I have been able to prove in 

 young synangia of this type that the tissue which would normally form 

 the septum may be sporogenous ; this is exactly the converse of what 

 has been proved by Goebel in Isoetes, and the conclusion which may 

 be drawn is that there is no essential difference between the tissue which 

 will form septum or trabeculcB and that which will form spores, since 

 they can mutually undergo conversion. 



It has already been shown by others that in Psilotum the number 

 of loculi in the synangium may vary, being sometimes two, normally 

 three, but occasionally four or five. In Tmesipteris it may be one, 

 two, or three; and as there is no doubt of the hornology of these 

 within the Psilctacese, we may conclude that in homologous parts the 

 loculi may vary in number- from one upwards. 



We may recognise within the sp'ecies Tmesipteris a correlation of 

 size to number of loculi ; the smallest specimens have no septum, 

 and these are produced at the limits of the fertile zone, where nutri- 

 tion may be failing ; those which are of normal size have two loculi : 

 occasionally, when of large size and well nourished, as at the middle 

 of the fertile zone, the loculi may be three. Here is illustrated in one 

 species much the same sequence as is seen elsewhere for distinct 

 genera, such as Lycopodium, Isoetes, Lepidodendron : where the 



