44 



NATURE 



[November ii, 1697 



l^aticheria, such species as V. repens and V. orntthocephala, 

 where the antheridia and oogonia are developed near each 

 other on the same thread. With weak light, especially 

 artificial light, the oogonium begins first to degenerate. He 

 never succeeded in suppressing the antheridia and at the same 

 time to produce oogonia. 



High temperature, low air pressure or weak light, tend to 

 suppress the oogonia, and at the same time the antheridia may 

 increase so that the number in a group is quite large, while the 

 oogonium degenerates or develops vegetatively. Klebs con- 

 cludes from his experiments that the causes which lie at the 

 bottom of the origin of sex in Vaucheria, as in other organisms, 

 are shrouded in the deepest mystery. 



In the higher plants a number of experiments have been 

 carried on for the purpose of learning the conditions which 

 govern the production of staminate and pistillate flowers, or in 

 other words the two kinds of sporophylls. From numerous em- 

 pirical observations on dioecious Spermatophyta, the inference 

 has generally been drawn that nutrition bears an important re- 

 lation to the development of the staminate and pistillate flowers ; 

 that scanty nutrition produces a preponderance of staminate 

 plants, while an abundance of nutrition produces a preponder- 

 ance of pistillate plants. For a period covering three decades 

 several investigators have dealt with this question experiment- 

 ally, notably K. Miiller, Haberlandt, and Hoffmann. These 

 experiments in general give some support to the inferences from 

 observation, yet the results indicate that other influences are 

 also at work, for the ratios of preponderance either way are not 

 large enough to argue for this influence alone. In a majority of 

 cases thick sowings, which in reality correspond to scanty nutri- 

 tion, tend to produce staminate plants ; while thin sowings lend 

 to produce pistillate plants. In the case of the hemp {Cannabis 

 saliva), Hoffmann found that these conditions had practically no 

 influence. He suggests that the character of each may have 

 Ijcen fixed during the development of the seed, or even that it 

 may be due to late or early fecundation. 



In monoecious plants it has often been observed that pistillate 

 flowers change to staminate ones and vice versd, and in dioecious 

 plants pistillate ones sometimes are observed to change to 

 staminate ones (the hemp for example, see Nagel, 1879). K. 

 Miiller states that by scanty nutrition the pistillate flowers of 

 Zeamays can be reduced to staminate ones. 



Among the pines what are called androgynous cones have 

 in some instances been observed. In Finns rigida and P. thun- 

 betgii, for example, they occur (Masters). Natsuda has de- 

 scribed in the case of Finns densijlora of Japan, pistillate and 

 androgynous flowers which developed in place of the staminate 

 flowers, and conversely staminate and androgynous flowers in 

 place of pistillate ones. Fujii has observed that where the pis- 

 tillate or androgynous flowers of Finns densijlora occur in place 

 of the staminate ones, they are usually limited to the long shoots 

 which are developed from the short ones of the previous year. 

 The proximity of those transformed short shoots (Kurztrieb) to 

 injuries of the long ones, suggested that the cutting away of the 

 long ones might induce the short ones to develop into long ones, 

 and the flowers which were in the position for staminate ones to 

 become pistillate. 



Fujii says, "In fact, the injuries producing such effect are 

 frequently given by Japanese gardeners to the shoots of the year 

 of Finns densijiora in their operations of annual pollarding. 

 But the ' Langtrieb ' which is transformed from a ' Kurztrieb ' 

 of the last year does not necessarily bear female of hermaphro- 

 dite flowers in the positions of male flowers." To determine 

 the influence of pollarding of the shoots he carried on experi- 

 ments on this pine in the spring of 1895. He pollarded the 

 shoots, so that, as he terms it, to induce the nourishment to be 

 employed in the development of the flowers and short shoots 

 near the seat of injury. In other cases one or two shoots 

 were preserved while all the adjacent shoots of last 

 year's growth at the top of the branch were removed, 

 and, further, both of these processes were combined. Out of the 

 forty-five branches experimented on, and on which there were 

 no signs of previous injury, there were nine pistillate or andro- 

 gynous flowers in place of staminate ones ; in twenty-one 

 branches with signs of previous injury, five were transformed, 

 while in 2283 not experimented on, and with no signs of previous 

 injury, only seven were transformed. Such abnormal flowers, 

 then, are due largely to the injuries upon the adjacent shoots, 

 and, Fujii thinks, largely to the increased amount of nourish- 

 ment which is conveyed to them as a result of this. 



NO. 1463, VOL. 57] 



From the experiments thus far conducted upon the determina- 

 tion of sex in plants or upon the determination of staminate or 

 pistillate members of the flower, nutrition has at least some in- 

 fluence in building up the nourishing tissue for the two different 

 organs or members. This can in part be explained on the 

 ground that antheridia and staminate members of the plant are 

 more or less short-lived in comparison with the archegonia and 

 pistillate members, the latter requiring more bulk of tissue to 

 serve the purpose of protection and nourisnment to the egg and 

 embryo. It is thus evident that while some progress has been 

 made in the study of this question, we are far from a solution of 

 it. Experiment has proceeded largely from a single standpoint, 

 viz. that of the influence of nutrition. Other factors should be 

 taken into consideration, for there are evidently other external 

 influences and internal forces which play an important rdle, as 

 well as certain correlation processes perhaps connected with the 

 osmotic activities of the cell sap. 



The relation of the parts of the flower to the foliage leaves is 

 a subject which has from time to time called forth discussion. 

 That they are but modifications of the foliage leaf, or con- 

 stituents cf the leaf concept, is the contention of the meta- 

 morphosis theory, and that the so-called sporophylls are modi- 

 fied foliage leaves is accepted with little hesitation by nearly all 

 botanists, though it would be very difficult, it seems to me, for 

 any one to present any very strong argument from a phylo- 

 genetic standpoint in favour of the foliage leaf being the primary 

 form in its evolution on the sporophyte, and that the sporophyll 

 is a modern adaptation of the foliage leaf. Numerous cases are 

 known of intermediate forms between sporophylls and foliage 

 leaves both in the Spermatophyta and Pteridophyta. These are 

 sometimes regarded as showing reversion, or indicating atavism, 

 or in the case of some of the ferns as being contracted and 

 partially fertile conditions of the foliage leaf. There has been a 

 great deal of speculation regarding these interesting abnormal 

 forms, but very little experimentation to determine the causes 

 or conditions which govern the processes. 



In 1894 I succeeded in producing a large series of these inter- 

 mediate forms in the sensitive fern {Onoclea sensibilis). The 

 experiments were carried on at the time for the especial purpose 

 of determining whether in this species the partially developed 

 sporophyll could be made to change to a foliage leaf, and yet 

 possess characters which would identify it as a transformed 

 sporophyll. The experiments were carried on where there 

 were a large number of the fern plants. When the first 

 foliage leaves were about 25 cm. high, they were cut 

 away (about the middle of May). The second crop of 

 foliage leaves was also cut away when they were about the 

 same height during the month of June. During July, at the 

 time that the uninjured ferns were developing the normal sporo- 

 phylls, those which were experimented upon presented a large 

 series of gradations between the normal sporophyll and fully 

 expanded foliage leaves. Among these examples there are all 

 intermediate stages from sporophylls which show very slight 

 expansions of the distal portion of the sporophyll, and the distal 

 portions of the pinnre, until we reach forms which it is very 

 difficult to distinguish from the normal foliage leaf. Accom- 

 panying these changes are all stages in the sterilisation of the 

 sporangia (and the formation of prothalloid grov^'ths), on the 

 more broadly expanded sporophylls there being only faint 

 evidences of the indusia. 



The following year (1895) similar experiments were carried on 

 with the ostrich fern {Onoclea struthiopleris), and similar results 

 were obtained. At the time that these experiments were 

 conducted, I was unaware of the experiments performed by 

 Goebel on the ostrich fern. The results he reached were the 

 same ; the sporophyll was more or less completely transformed 

 to a foliage leaf. Goebel regards this as the result of the 

 correlation process, and looks upon it as indicating that the 

 sporophyll is a transformed foliage leaf, and that the experi- 

 ment proves the reality here of the modification which was 

 suggested in the theory of metamorphosis, and thus the foliage 

 leaf is looked upon by him as the primary form. Another inter- 

 pretation has been give'n to those results, viz. that they 

 strengthen the view that the sporophyll, from a phylogenetic 

 standpoint, is primary, while the foliage leaf is secondary. What 

 one interprets as a reversion, another regards as indicating a 

 mode of progress in the sterilisation of potentiality, sporogenous 

 tissue, and its conversion into assimilatory tissue. It is perhaps 

 rather to be explained by the adaptive equipoise of the corre- 

 lative processes existing between the vegetative and fruiting. 





