290 



SCIENCE. 



[N. S. Vol. I. No. 11. 



which no seedling plants were concerned. 

 If all the common garden strawberries owe 

 their origin to a Hke source — as I cannot 

 doubt — then we have here a most instruc- 

 tive case of sexless evolution, but one in 

 which the subsequent generations reproduce 

 these characters of sexless origin by means 

 of seeds. 



This asexual modification is not confined 

 to domesticated plants. Any plant which 

 is widely distributed by man bj^ means of 

 cuttings or other vegetative parts may be ex- 

 pected to vary in the same manner, as much 

 experiment shows ; and if they behave in 

 this way when disseminated by man they 

 must undergo similar modification when 

 similarly disseminated by nature herself. 

 I need only cite a few instances of habitual 

 asexual distribution of wild plants to recall to 

 your attention the fact that such means of 

 distribution is common in nature, and that in 

 some cases the dispersion over wide areas is 

 quite as rapid as b}^ means of seeds ; and 

 some plants, as various potamogetons, cera- 

 tophyllums and other aquatics, are more 

 productive of detachable winter buds and 

 other separable vegetable organs than they 

 are of seeds. The brittle willows drop theu* 

 twigs when injured by storms of ice or 

 wind, or hy animals, and many of these cut- 

 tings take root in the moist soil, and they 

 may be carried far down streams or distrib- 

 uted along lake shores ; the may-apple and 

 a host of rhizomatous plants march onward 

 from the original starting point ; the brj'- 

 ophyllum easily drops its thick leaves, each 

 one of which may establish a new colony of 

 plants ; the leaves of the lake-cress (Nas- 

 turtium lacustre) float down the streams 

 and develop a new plant while they travel ; 

 the house-leeks surround themselves with 

 colonies of ofi^-shoots, the black raspberry 

 travels by looping stolons, and the straw- 

 berry by long runners ; the tiger-lily scat- 

 ters its bulb-like buds, and all bulbiferous 

 plants spread quite as easily by their fleshy 



parts as by seeds. Now all these vegetative 

 parts, when established as independent 

 plants, produce flowers and good seeds, and 

 these seeds often perpetuate the verj' char- 

 acters which have originated in the asexual 

 generations, as we haA'e seen in the case of 

 many bud-varieties ; and it should also be 

 remarked that these phj-tons usuallj^ trans- 

 mit almost perfectly the characters acquired 

 by the plant from which tliej' sprung. Or, 

 to put the whole matter in a convenient 

 phrase, there may be, and is, a progi-essive 

 evolution of plants without the aid of sex. 

 Now, where is Weismann's germ-plasm? 

 One of the properties of this material — if an 

 assumption can receive such designation — 

 is its localization in the reproductive organs 

 or parts. But the phyton has no reproduc- 

 tive parts ; or, if it has them, they are de- 

 veloped after the phyton has lived a per- 

 fectly sexless life, and possibly after genera- 

 tions of such life, in which it and its progeny 

 may either have remained comparatively 

 stable or may have varied widely, as the 

 circumstances may have determined. If 

 any flower, therefore, contains germ-plasm 

 it must have derived it out of the asexual 

 or vegetative or soma-plasm. And I mU 

 ask where the germ-plasm is in ferns. 

 These plants are fertilized in the prothallic 

 stage, and one brief sexual state is all that 

 the plant enjoj^s, after which the sex-organs 

 die and whollj' disappear. The fern, as the 

 laj^man knows the plant, is whollj^ asexual, 

 and the spores are as sexless as buds ; yet 

 these spores germinate and give rise to an- 

 other brief prothaUic or sexual stage, and if 

 there is any germ-plasm at all in these 

 fleeting sexual organs it must have come 

 fi-om the sexless spores. It is interesting 

 to note, in this connection, this bud-varia- 

 tion is as frequent in ferns as in other 

 plants. Or, if the Weismannians cau locate 

 the germ-plasm in all these instances, pray 

 tell us where it is in the mja-iads of sexless 

 fungi ! There is no such thing as continu- 



