BOTANICAL .SL'BJKCTS. 363 



illustration of a clatlopliyl. It has a central niidrib, and alternate 

 side nerves (really what are called branches), ending in the inden- 

 tations or axillae of the margins, out of which branches arise just 

 as they do in the BryophyUum leaf. 



Eighth. — That there is no essential difference between the 

 stem and the root. The one may be regarded as a continuation of 

 the other, or both as two branches emerging from the same point. 

 It is impossible to regard them as different when both the one and 

 the other give off buds and roots. Both are suckers of material 

 from the outside, and each helps the other in its groAvth. It 

 follows that the sub-dix-isions of the main root correspond to the 

 sub-divisions of the main stem, which are the leaves and Ijranches. 

 The media in which they grow, and heredity, determine the 

 character which these two forms will take on. The leaves of 

 Nigella damascena are only distinguishable from roots by their 

 being green. 



Ninth. — That the tendrils of Vitis, Cucurbita, and others 

 occupy the position of aerial roots rather than other organs, that 

 is, they are roots of attachment rather tlian roots of absorption. 

 This is well exempliiied in the aerial roots of orchids, and more 

 especially in those of the Vanilla planifolia, the aerial roots of 

 which act as tendrils to the slender stem. Some tendrils might 

 perhaps be considered as branches, such as those of Passifiora, 

 which are often axillary, but the tendril at a node admits of dis- 

 placement, and it is often impossible to .say whether it is a stipule, 

 a leaf, a branch, or a root. As, however, in these Notes I have 

 regarded roots, leaves, and branches as homologous, it makes little 

 difference whether a tendril be regarded as the one or the other. 

 What I think we should fix in our mind is that in seaweeds there 

 are roots of attachment only, and roots of attachment and absorp- 

 tion ; and this same organ witli a differentiated fu]iction ajjpears to 

 have been inherited by phaenogams, which produce in similar 

 situations roots with the function of tendrils. 



Tenth. — That tlie stamen is a leaf or cladophyl, the Ulameut 

 corresponding to a jictiole, and the anther to a l)lade. The jwllen 

 appears to admit of various interpretxitions : — 



(n^) It may lie considcre«l as the male element derived from 

 the ])lade of a seaweed, such as that of Cutler ia 



