Seedling Structure of Gymnosperms. IV. 329 
four are produced and are arranged in two pairs, the units of each of which 
join together in the hypocotyl, so that, from this level downwards, the 
appearance is remarkably like that of Ephedra ; finally, in Gnetum , the 
bundles are very numerous in the blade of each seed-leaf; the petiole, how¬ 
ever, contains five which, by fusion, may be reduced further, so that either 
four or five bundles enter the axis. 
Comparing the Gnetales with other Gymnosperms, it is seen that the 
transition-phenomena exhibited by these plants resemble those of the 
Podocarpeae 1 and the Araucarieae, 2 the similarity between which two 
groups has already been remarked upon. Ephedra is practically identical 
with Podocarpus , the only difference being that in the former plant the 
transition is slower, taking place in the lower region of the hypocotyl. The 
same observations apply equally well to Welwitschia , although the resem¬ 
blance is masked by the larger number of cotyledonary traces ; still more 
so is this the case in Gnetum. 
A comparison with the Araucarieae shows, with regard to the features 
under discussion, that Welwitschia is very like indeed to Araucaria 
Cunninghamii. The resemblance between Ephedra and Gnetum on the 
one hand, and the Araucarias on the other, is, on a superficial examination, 
less well marked owing to the fewer number of seed-leaf-traces in Ephedra , 
and to the numerical increase and anastomoses, within the hypocotyl, of 
these structures in Gnetum. The comparison of the critical stages, how¬ 
ever, reveals the similarity between these plants. There is also a resemblance 
between Welzvitschia and Ginkgo, and Gnetum and certain Cycads, as 
regards the number of bundles in the cotyledons, but the behaviour of 
these strands in the transition region is, however, not the same. 
The present paper concludes the statement of our observations on the 
seedling structure of the Gymnosperms, and incomplete though it be, 
it would have been impossible to have considered the subject even thus 
fully without the co-operation of many in supplying us with material. 
To the following we wish to render thanks and to express our apprecia¬ 
tion of their kindness :— 
The Directors of the Botanic Gardens of Brisbane, Buitenzorg, Kew, 
Peradeniya, and Sydney ; Mr. Boodle, Mr. de Fraine, Prof. H. H. W. 
Pearson, Dr. D. H. Scott, Mr. Tansley, and Miss Thomas. 
More especially are we indebted to Mr. Hales, the Curator of the Old 
Physic Garden, Chelsea; and him we desire particularly to thank, not only 
for material, but also for the trouble and care he has taken in the germina¬ 
tion of our seeds. 
Our general conclusions will appear later on, when our work on certain 
Angiosperms is completed. 
A correction. —In Part III, p. 434, it is stated that Sprecher does not 
1 Part I (Annals, xxii, 1908). 2 Part II (Annals, xxiii, 1909). 
