396 General Notes. [May, 



each other. Lichenes are reckoned as intermediate between the 

 other two classes of Thallophytes ; but all the limits are uncer- 

 tain." As to the now famous question regarding the autono- 

 my of lichens, after describing hyphae and gonidia, we find (p. 

 vi.) " But we are not quite at liberty to stop here. The marked 

 contrast of hypha and gomdium was open to a hypothetical ex- 

 planation, based on the apparent relations of these organs to what 

 seemed the same in other classes of Thallophytes, which suggested 

 and had its exemplification in the memorable labor of Schwen- 

 dener. This was met, however, by lichenologists in a manner 

 and tone often ill enough corresponding with the simply objective 

 position of the other side ; and there was room for further inves- 

 tigation. Ideally, from the point of view of those who look at 

 lichens as autonomous, the primordial cell should be referable 

 either to hypha or gonidium ; but, in fact, as well emphasized by 

 Minks, it is its dualism which, from the beginning of our knowl- 

 edge, and through all its extent, characterizes the lichen struc- 

 ture, and determines its historv. Yet this is not all. The pene- 

 trating glance of the cited vegetable anatomist has demonstrated 

 the existence of a third element. Behind and before the manifes- 

 tation of the hyphae, which are to play so great a part in the 

 lichen world, is a dimly seen, primordial tissue, a web or net-work 

 of exceedingly delicate filaments (Hyphema Minks), which grad- 

 ually pass into the hyphae proper, as these accomplish their high- 

 est result in generating the gonimous cells." 



On the terms Annual and Biennial. — There is certainly much 

 ambiguity in the terms annual and biennial. Those plants which 

 germinate in the spring and die in the autumn are not 

 very different from those which vegetate in the summer or au- 

 tumn, and flower and die in the succeeding spring or summer ; 

 nor indeed can I see much between them and plants like Agave, 

 which live in a barren state for many years, and then flower once 

 and die. It seems to be only a question' of the time required to 

 concentrate the requisite energy to produce flowers and fruit. 

 True annual plants may be divided into winter annuals and sum- 

 mer annuals. The former usually store up nutritive matter in the 

 autumn to supply the flowering state in the spring; differing in 

 this from summer annuals. But this is not constantly the case. 

 The Agave is many years doing this. Although this plant flow- 

 ers only once, we of course ought to have a term to distinguish 

 it from the annuals. There are also the plants which produce 

 stoles rooting at the end, such as the sympodes of Fragaria ; in 

 that case the plants are truly perennial. But see such plants as 

 Epilobium, where the buds at the end of stoles alone remain 

 alive during the winter, and produce the plants of the succeeding 

 year : what are we to call these ? We usually denominate them 

 perennial. Then how separate them from those which are not 

 aerial, but go through the same course ? Then come such plants 



