Anatomy of Terdtological Seedlings . IV. 489 
which normally produces three strands, should only produce two, and the 
other, which normally produces none, should also produce two, and further 
why the bundles of the two * cotyledons ’ should together produce a vascular 
condition essentially similar to that of the normal monocotyl. Another 
difficulty is encountered in the position of the first epicotyledonary leaf, 
which, in the dicotyl, lies in the plane at right angles to the median plane 
of the two ‘ cotyledons \ 
Now where only one cotyledon elongates the median plane of the first 
epicotyledonary leaf corresponds to that of the two ‘ cotyledons \ If there- 
fore the dicotyledonous condition is the result of the equal development 
of the two growing points which, according to Coulter and Land, are 
normally present in Monocotyledons, it has been accompanied by a shifting 
through 90 ° of the insertion of the first leaf, a phenomenon which seems 
somewhat unlikely. The alternative explanation is that the dicotyledonous 
seedling has arisen by the qualitative fission of a normally single cotyledon. 
In such a case each half-cotyledon would contain two bundles, namely one 
lateral and half the midrib bundle, and these would behave in transition like 
the bundle system of the undivided cotyledon, precisely as they do in the 
seedling under discussion. It is notevvorthy in this connexion that the 
median cotyledonary bundle normally produces two widely divergent half- 
bundles prior to the constitution of the cotyledonary plate, so that complete 
division would only be an extension of such a process. Granted the 
accuracy of this interpretation the orientation of the first epicotyledonary 
leaf is seen to be perfectly normal, a view which is confirmed by the 
relationship of its vascular strands with those of the two cotyledonary 
members. With regard to the theoretical construction placed upon the 
embryonic structure of Cyrtanthus sanguineus it would appear that some 
knowledge of the earlier phases of embryogeny is desirable, since the 
shallow apical lobing of the younger of the two stages figured by Miss 
Farrell (12) may be interpreted with equal plausibility as the result of the 
development of four procambial strands rather than as the cause of their 
development. Finally, with regard to the conception of the epiblast of the 
grass embryo as a cotyledon, one would expect, if this were the case, to 
find at least some evidence of vascular tissue where this structure is well 
developed. Actually there is no trace of such tissue, unless the small 
meristematic group of cells opposite the scutellum in the maize, a form in 
which the epiblast is absent, be interpreted as such. Here too, as in 
previous cases, the position of the first epicotyledonary leaf offers a difficulty 
which Coulter does not attempt to explain. It seems to us, therefore, that, 
taken as a whole, the evidence submitted in support of this theory is of too 
flimsy and too equivocal a character to be entirely trustworthy, and certainly 
does not appear to provide an adequate foundation upon which to erect the 
imposing superstructure for which its authors have intended it. 
