144 STUDY OP COMMON PLANTS. 



food materials. The whole structure shows a likeness on the one 

 hand to the spores of other vascular cryptogams, and on the other 

 to the embryo-sac of flowering plants. 



RELATIONSHIP. 



It is desirable tliat at least the external characters and 

 fructification of one or more additional genera of vascular 

 cryptogams should be studied in connection with the pre- 

 ceding ones ; but specific directions are omitted, partly 

 because of uncertainty as to material likely to be procura- 

 ble, and partly because it is understood that by this time 

 the student should be in a position to make an intelligent 

 comparative study of at least the general characters of 

 any group to which he has already given special attention. 

 Club-mosses are as likely to be available as any of the 

 Lycopodineee, since they are pretty widely distributed, and 

 besides are extensively used for Christmas decorations. 

 As they appear in market in the middle of winter they 

 are frequently in fruit. Marsilia and Isoetes are of great 

 interest, and when they can be obtained may well claim 

 a considerable share of the time given to this group. 

 Aside from the manuals and text-books, the references 

 given below will be found serviceable to those who under- 

 take a further study of the vascular cryptogams.^ 



HEVIEVr AND SUMMARY. 



The vascular cryptogams mark an obvious advance 

 beyond the cellular cryptogams, manifested chiefly in the 

 development of well-defined fibro-vascular bundles, and in 



1 Campbell, Development of Pilularia globuUfera, L., Annals of 

 Botany, Vol. II, p. 233 ; Contributions to the Life-History of Isoetes, 

 Annals of Botany, Vol. V, p. 231 ; On the Prothallium and Embryo of 

 Osmunda Claytoniana, L., and 0. cinnamomea, L., Annals of Botany, 

 Vol. VI, p. 49 ; On the Affinities of the Filicineoe, Botanical Gazette, 



