450 Scott and Hilt .— Strnctui'e of Isoetes Hystrix. 
the desire to find a heterosporous representative of the 
Eusporangiate Ferns. 
Mr. Wilson Smith, in his recent paper, has stated with much 
force the arguments for the Lycopodinean affinities of Isoetes , 
In addition to points which we have mentioned above, he calls 
attention to the extremely early development of the spor¬ 
angium in Isoetes , to its multicellular archesporium, and its 
indehiscent character. 
As to the position of Isoetes within the Class Lycopodiales, 
the genus appears to have some real affinity with Selagi- 
nellci , though not close enough to render it desirable to keep 
them in the same Family. The relationship of Isoetes to the 
Lepidodendreae is probably a nearer one h It may possibly 
turn out that the curious Triassic genus Pleuromeia , of which 
we have recently had a full description from Count Solms- 
Laubach (1899), may have been in some respects inter¬ 
mediate between the arborescent Palaeozoic Lycopods and the 
reduced genus Isoetes. We have not thought it necessary 
to discuss certain resemblances which have been suggested 
between Isoetes and the Monocotyledons. Much further 
evidence will be required before these apparent points of 
similarity can be accepted as any indication of affinity. 
1 On this point compare Bertrand Cornaille et Hovelacque, Remarques 
sur la Structure des Isoetes. Saint-Etienne, 1897. 
