944 



SCIENCE. 



[N. S. Vol. V. No. 129. 



were a normal growth of the plant, and 

 which yet, as Molliard has pointed out, pro- 

 duces formations different from the normal 

 tissues, is proof that the protoplasmic reac- 

 tion of somatic cells to definite chemical 

 stimuli is as exact as it is profound. To cite 

 one concrete example from many that Mol- 

 liard gives, it can be said that Arahis sagittata 

 when attacked by an Aphis shows : — 



(a) An abundance of hairs of special 

 form on all the organs. 



(b) A coloration due to a pigment-liquid 

 in the epidermal cells. 



(e) Longer life of the floral organs. 



(cZ) Hypertrophy of cells. 



(e) Transformation of tissue of varied 

 consistency, into a uniform parenchyma. 



(/) Death of the sexual cells. 

 In a condensed paper like this it is impos- 

 sible to touch on such subjects as the 

 origin and transmission of plant colors, 

 of many heterophyllous modifications, of 

 floral numbers and of floral form, nor can 

 we treat of plant hybrids, of which proba- 

 bly 6,000-7,000 are now known. 



I would sum up the position by saying 

 that, while in the earlier illustrations used 

 by me evidence was advanced which fa- 

 vored the idea of characters being acquired 

 even in the life-time of an individual 

 and that represented direct environmental 

 adaptation, in later illustrations, such as 

 those furnished by some xerophilous, some 

 domatial, many cultivated and a grafted 

 plant, direct proof exists of acquired char- 

 acteristics that are hereditarily transmitted 

 by seed. I have not considered it neces- 

 sary to speak of bud variations and their 

 seminal reproduction, as these have been 

 so fully dwelt on by Darwin and recently 

 by .Bailey. The N"eo-Darwinian position 

 seems to me superfluous, because it explains 

 nothing on an exact basis of cause and 

 efiect. It is easy to say, when variations 

 or evidences of new adaptability appear in 

 a plant, that these are but the expression of 



previously latent potentialities, or of varia- 

 tions first contracted or assumed by the germ 

 plasm, and that subsequently exhibit them- 

 selves in the somatoplasm. Possibly were 

 the eyes of our understanding enlightened 

 we might discover the budding possibilities 

 of an orchid or an oak in an alga, but before 

 accepting such possibilities it may be well 

 to see whether the Lamark-Darwinian prin- 

 ciples cannot guide us perfectly and suffi- 

 ciently far. Here, however, I would sug- 

 gest, in contradistinction to Wallace, that 

 indefinite variation must be allowed for. 

 Every plant is a structure built up of ex- 

 tremely complex chemical bodies that are 

 being acted on by external and internal 

 stimuli. "We can scarcely suppose that 

 new or modified stimuli are always produc- 

 tive of good and good only. Eather should 

 we consider that in each little plant world, 

 as in our larger physical world, volcanic ex- 

 plosions occur that are in one sense a 

 source of safety for the future, but which 

 leave behind beds and streams of debris 

 that may be useless or even destructive. 

 Various of the plant colors, resins, crystals 

 and other frequent compounds may be ex- 

 plicable primarily as side issues that were 

 for the time useless, even though, as in the 

 compounds just named, we find that they 

 now function beneficially in the plant 

 economy. 



Every candid examiner of the facts must 

 admit, however, that sudden and several 

 variations often appear in individuals placed 

 side by side with their like that show no 

 change. I do not see that we possess at 

 present a sufiBciently exact knowledge of all 

 the possible factors that may start variation 

 to enable us to explain these. Still this 

 should be no deterrent to our accepting the 

 position that generally explains ascertained 

 facts of structure and function. 



It now remains for me to say a few words, 

 as a student of plant cytology, on some of 

 the theories that have been advanced to ex- 



