732 Hens low, — The Origin of Monocotyledons from Dicotyledons , 
of all aquatic Dicotyledons and of all Monocotyledons, whether aquatic or 
terrestrial. This was known to Richard and Poiteaux in 1808. 
This difference, as well as others, is well seen in dicotyledonous amphi¬ 
bians, such as Bidens cernna} 
It has long been recognized that a characteristic feature of Monocotyle¬ 
dons, in addition to the arrest of the primary root, is to have the root-cap 
together with its formative tissue distinct from that of the root behind it. 2 
Numerous experiments with seedling Dicotyledons germinating in water, 
not only invariably showed the arrest of the primary root, with the evolu¬ 
tion of secondary or adventitious ones ; but as one of the latter grows from 
a lateral papilla, with a common meristem, this latter contracts, as it were, 
often appearing as pointed, with the calyptra of about four layers, more or 
less perfectly distinct from the root. If the complete separation is not 
always fully secured at first, the tendency to divide the merismatic tissue 
is always present. If sufficient time be allowed before examination, the 
calyptra becomes distinct. 
Miss Sargant calls attention to the ‘ Absence of a true epidermis in the 
root above the root-sheath in Monocotyledons \ This character of the root is so 
far as we know universal among Monocotyledons, but not confined to them. 
It is found in the Nymphaeaceae. 3 Since the degradation of the epidermis to 
the epithelioid state is characteristic of all submerged plants, the above loss 
is probably a further instance of the original effect of water. 
12. Origin of the formerly called ‘Endogenous 5 Arrangement 
OF THE CAULINE BUNDLES OF MONOCOTYLEDONS. 
Professor Vines observes 4 : ‘In Schizostely the single primitive stele 
breaks up into as many distinct strands as it possesses vascular bundles . . . 
each schizostele being invested by its own segment of the endodermis. 
This obtains among Phanerogams in the Nymphaeaceae, some species of 
Ranunculus , as R. aquatilis and R. Lingua, &c., and in the Monocotyledons 
Hy dr ode is and Limnocharis (Alismaceae). 
c Stems with cauline bundles may be monostelic or polystelic ; mono- 
stelic stems with cauline bundles are generally gamodesmic, having a solid 
vascular cylinder, e. g. Lycopodium, some aquatic Dicotyledons, e. g. Utricu - 
laria , Aldrovanda , Calii trie he, Myriophyllum , Ceratophyllum ; some aquatic 
Monocotyledons, e. g. E lode a, Hy dr ilia, &c .’ 5 
1 I have described and figured the two kinds of roots in this plant, the Bur-Marigold, in 
my Heredity of Acquired Characters in Plants (Murray). 
2 loc. cit., p. 507. 
3 Theory of the Origin of Monocotyledons, etc. Ann. Bot., xxvii, p. 83. 
4 Students’ Text-Book of Botany, i. 152. 
5 Ibid., p. 173. It will be noted that the above quotations only prove that water affects 
Dicotyledons and Monocotyledons alike. But the object of this paper is to show that precisely the 
same results are now to be seen in terrestrial Monocotyledons, whose aquatic ancestors have re¬ 
turned to land. 
