Dec. 27, 1877] 



NATURE 



159 



comes a preliminary instead of a purely professional study 

 by becoming more diffused, a greater taste for the subject 

 may arise. 



Prof. Pringsheim contributes th'e first paper, one part 

 dealing with the interesting subject of the budding of the 

 fruit of mosses, the second on the alternation of genera- 

 tion in the Thallophytes, a subject suggested by the first 

 part. If the seta of the ripe fruit of the moss be cut into 

 pieces, and the pieces cultivated on wet sand, protonema 

 threads will grow from the cut portions, and produce the 

 usual buds, exactly Uke protonema threads developed 

 from the spores or stem and leaves of mosses. The 

 anatomical connection of the protonema with the tissue 

 of the seta can be observed in good longitudinal sections. 

 Not all the cells can give rise to protonema, but only those 

 of the middle zone, situated between the peripheral 

 cortical cells and the central bundle. These cells contain 

 abundance of reserve matter, such matter being found in 

 many parts of the moss-fruit. The product of protonema 

 by the seta of the moss is to be compared to the budding 

 of the prothallium of ferns described by Farlow. Prings- 

 heim figures in the two plates illustrating the paper, the 

 protonema developing from the seta of Hypniim serpens^ 

 H. cupressiforme^ and Bryum caespitosiim, and he shows 

 the stem and seta to be identical structures. 



The second part of the paper, on the alternation of 

 generation in Thallophytes, is difficult to follow without 

 illustrations, as it takes for granted that the reader is 

 acquainted with all the recent researches on the lower 

 plants. Pringsheim distinguishes between sexual alterna- 

 tion of generations and vegetative alternation of genera- 

 tions (sprosswechsel), the fructification and vegetative 

 propagation. AH the generations of Thallophytes (as 

 well as of the Cormophytes) begin with one free cell (the 

 spore). The generations in the Thallophytes represent 

 free individual plants, while in the Cormophytes the 

 generations remain in organic connection and in their 

 individual sequence appear only as two portions of one 

 series of developments. From this it follows that the 

 " fruits " of Thallophytes never have the value of a 

 " generation," and also that where the development is due 

 to sexual influence, they are only sexually influenced 

 organs of the female plant. Such parts are the fruits of 

 Floridece, also apparently the Perithecia and Apothecia of 

 Ascomycetes, which do not behave differently from the 

 calyptra of the moss or the thickened tissue (gewebe- 

 polster) of the prothallum, in which the embryo of the 

 vascular cryptogams is developed. Pringsheim believes 

 that in the trichogyne and ascogon the influence of 

 fertilisation is spread from cell to cell until it reaches the 

 spores, just as in mosses and ferns the reverse process 

 occurs, and the influence spreads from the fertilised 

 germinal cell to the archegonium. Carpospores and asco- 

 spores are therefore to be regarded not as sexually- 

 produced spores of a sexually-produced generation, but 

 as truly sexually-produced spores, developing in the 

 sexually- influenced organ of the mother plant. 



The second paper, illustrated by two plates of diagrams, 

 and occupying nearly half the part, is by F. G. Stebler, 

 " Researches on Leaf-growth." The numerous obser- 

 vations made on A Ilium Cepa, Secale cereale, T^'iticmn vul- 

 var e, Cucurbita melanospertna, are detailed at full length, 

 and the following summary of the result of the paper is 



given at the conclusion. The leaf begins to grow very 

 slowly, then growth becomes more rapid until a maximum 

 of rapidity is reached ; then growth becomes slower and 

 slower until at last it ceases. The leaf thus behaves like 

 other growing parts of plants. The growth of the linear 

 monocotyledonous leaf is basipetal. The apex zone of 

 the leaf ceases earliest to grow, then succeeding zones in 

 basipetal order, until lastly the growth of the basal zone 

 terminates the growth of the entire leaf. Most produc- 

 tive of increase in length is the growth in the basal zone, 

 but at different times the maximum activity is in different 

 zones, the absolutely greatest zone of growth proceeding 

 in succession from the upper part of the leaf to the lower. 

 The maximum period of growth of the whole leaf is the 

 sum of the maximum periods of all the zones. 



The linear monocotyledonous leaves examined in 

 reference to alternations of growth by day and night 

 showed a daily periodicity of growth, the growth dimi- 

 nishing as the intensity of the light diminishes. The 

 maximum of growth corresponds to the greatest intensity 

 of light ; the minimum is observed to occur shortly before 

 sunrise. The cause of the daily periodicity of growth is 

 assimilation ; as assimilation increases the growth in- 

 creases ; as it diminishes the growth diminishes. 



The same daily periods of growth were observed in 

 etiolated linear monocotyledonous leaves in the dark, the 

 external conditions being constant. The periodicity has 

 thus been transmitted. 



In the dicotyledonous leaves observed the daily periods 

 were modified, so that after the maximum of growth was 

 reached in the forenoon a retardation took place, and a 

 gradual diminution of the growth till the following morn- 

 ing before sunrise. At daybreak the growth rapidly 

 increases again to reach a maximum in the forenoon. If 

 the intensity of the light is small the maximum is later of 

 occurring than if the light be very intense. 



The maximum of the day periods of growth of the 

 dicotyledonous leaf is due to the assimilation. The retard- 

 ation during the day occurring after the maximum of 

 growth (but not the maximum of light) has been reached, 

 is due to the action of the light. 



The third paper occupying the remainder of the part is 

 by Dr. Celakovsky, and is entitled, " Teratological Con- 

 tributions to the Morphological Import of the Stamens." 

 It is illustrated by three plates. Considerable uncertainly 

 still exists as to the morphological value of the different 

 parts of the stamen, but more especially of the anther. 

 The difficulty does not exist in regard to the pollen- 

 bearing caulomes, but there are still difficulties in those 

 cases where the stamens are modified leaves. Whether 

 the question can be settled by the study of the develop- 

 ment alone is a matter of doubt, even after the valuable 

 researches of Warming and Engler on the subject ; and 

 it appears likely that the most important results may be 

 expected from the careful study of the numerous abnor- 

 malities of stamens so constantly met with. The scien - 

 tific study of the teratological developments of stamens 

 must therefore be looked upon as of the highest import- 

 ance, and Celakovsky — already well known by his tera- 

 tological researches, here describes and figures the 

 changes (phyllody) of the stamens of Rosa chinetisis, 

 Dictamnus albus, and in the double flower of Camellia 

 japonica. 



