October 21, 1897] 



NATURE 



601 



and does not take place in the mother-cell, but in the neck 

 joining it to the daughter-cell. When about to divide, the 

 nucleus places itself just at the opening of this neck, and pro- 

 ceeds to make its way through it into the daughter-cell, until 

 about half of it has passed through, when it divides completely, 

 and the two nuclei thus formed separate from each other towards 

 the opposite sides of their respective cells. 



The nuclei of Saccharomyces Ludwigii and S. Pastorianus 

 were also described. 



The process of spore- formation was observed in S. cerevisea. 

 In a cell about to sporulate the nucleus is found in the centre of 

 the cell, and appears to be homogeneous in structure. When 

 the nucleus divides its outline becomes irregular, and the 

 granules arrange themselves in the form of a short rod sur- 

 rounded by the other portion of the nucleus, which stains 

 differently and appears to form a structure of the nature of a 

 spindle. The granules separate into two groups, and each 

 group becomes a nucleus. The two nuclei thus formed again 

 divide, and four nuclei are produced, each of which becomes 

 the nucleus of a spore. A small quantity of protoplasm accu- 

 mulates round each nucleus, spore membranes appear, and four 

 spores are thus formed, standing in the remainder of the proto- 

 plasm, from which ultimately the thick spore membranes are 

 produced. 



The author referred to the process of nuclear division in spore- 

 formation as probably a simple form of karyokinesis. 



A disease of tomatoes, by W. G. P. Ellis. From diseased 

 tomatoes received in August 1896 from Jersey, the associated 

 fungi and bacteria were isolated and cultivated on nutrient 

 gelatine, and the mycelium was traced in sections of the fruits. 

 On removing the fruit skin with carefully sterilised instruments 

 the mycelium within the fruit formed in a short time the well- 

 known sporangiophores of Miuor stolonifer. Though late in 

 the season, infection of sound plants at the University Botanic 

 Gardens, Cambridge, from pure cultures caused a disease re- 

 sembling that of the fruits received in August and September 

 from the grojver. Experiments are in progress to determine 

 (i) whether the fungi obtained, other than Mticor stolonifer, 

 cause disease, and (2) the site of infection. 



Note on Pleurococciis, by Dorothea F. M. Pertz. Cultures 

 of Pleurococciis in nutritive solutions were made during the 

 winter months, from November to April. They did well in 

 Knop's solution, "2 per cent., in sterilised glass dishes and flasks, 

 which were placed m different situations : in the laboratory, in 

 a greenhouse, and out of doors. 



Separate clusters of Pleurococcus in hanging drops of the 

 same solution were also observed as continuously as possible. 

 These drops were suspended in carefully sterilised moist 

 chambers, which were kept for several weeks, in one case for 

 two months. 



The chief difficulties met with were, first, to obtain the Pleuro- 

 cocciis in absolutely pure condition, and then to keep it suffi- 

 ciently aerated without running any risk of making the culture 

 impure. Both the "globular sporangia" and those of "elong- 

 ated or quadrangular form," observed by Chodat, occurred 

 frequently, and they seem undoubtedly to be produced by the 

 transformation of normal Pleurococcus cells. Individual spor- 

 angia were repeatedly selected for special observation, and the 

 process by which they break up into separate spores was noted 

 at all its stages. 



The filamentous form described by Chodat never occurred. 



Prof. Farmer, in referring to Miss Pertz' experiments, 

 announced that he had succeeded in obtaining the filamentous 

 form of Chodat from Pleurococcus cells. 



Prof. Crookshank read a paper on Streptothrix actinomycotica 

 and allied species of Streptothrix, and Prof. Macallum, of 

 Toronto, contributed a paper on the origin of intracellular 

 organs. 



Vascular Cryptogams and Phanerogams. 



The gametophyte of Bolrychiuni virgittiamtm, by E. C. 

 Jeffrey. The author's researches were conducted on prothallia 

 of Botrychiutn obtained from several localities in the province 

 of Quebec and other parts of Canada. 



The gametophyte of B. virginiatiuin is of flattened oval shape, 

 2-18 mm. in length and I 5-8 mm. in breadth. The middle 

 of the upper surface is occupied by a well-defined ridge which 

 bears the antheridia. The archegonia are found on the de- 

 clivities which slope away from the antheridial ridge. The 

 lower part of the prothallium is composed of yellow tissue rich 

 in oil, the upper portion, on which the sexual organs are 



NO. 1460, VOL. 56] 



situated, is white in colour and free from oil. An endophytic 

 fungus, probably a Pythtum, occurs in the oily tissue. The 

 antheridia originate behind the growing-point from a single 

 superficial cell. The spermatozoids are large in size, but other- 

 wise resemble the ordinary fern type. This development ap- 

 pears to agree closely with that described in the Marattiacece 

 and Equisetacere. A young archegonium consists of three cells : 

 the most external gives rise to the neck, the middle cell to the 

 neck-canal-cell and the ventral cell, and the internal cell consti- 

 tutes the basal cell. The first division of the oospore is across 

 the long axis of the archegonium, the next division is parallel to 

 the long axis of the prothallium, and the third cross-wall is in 

 the transverse direction of the prothallium and at right angles 

 to the other two. The organs appear very late, and only after 

 the embryo has attained a large size. 



Remarks on changes in number of sporangia in vascular 

 plants, by Prof. F. O. Bower, F.R.S. Comparison shows that in 

 certain cases a progressive increase in number of sporangia has 

 taken place, in others a decrease. The changes may be classi- 

 fied as follows : — 



Increase in Number of Sporangia. • 



Directly i ^'^^ ^'^ septation of sporangia. 



^ ] (b) by interpolation of sporangia. 



I'(c) by continued apical or intercalary growth of the 

 part bearing the sporangia, with or without 



Indirectly 



j branching. 



\(d) by branchings in the non-sporangial region 



Decrease in Number of Sporangia. 



Directly I ^'^^ ^^ ^"^'°" of sporangia. 



^ \ {b) by abortion of sporangia. 



[(c) by reduction or arrest of growth or branching oi 

 Indirectly-' ^^'^ bearing the sporangia. 



^ j [d) by suppression of branchings in the vegetative 

 V region, resulting in fewer sporangial shoots. 



The author pointed out that the physiological condition of 

 the plant during development may largely determine the greater 

 or less prominence of any one factor ; he maintained that an 

 analytical study, such as the above, may afford assistance in 

 solving the problem of the origin of homosporous Pteridophyta. 



On spermatozoids in Zatiua inlegrifolia, by H. J. Webber. 

 Nfr. Webber gave a short account of his recent discovery of the 

 existence of large multiciliate spermatozoids in the pollen-lube 

 of Zainia inlegrifolia, a cycad which he investigated in Florida. 

 The facts brought forward by the author of the paper were of 

 exceptional interest ; he described the development of an 

 unusually large antherozoid from each of the daughter-cells 

 formed by the division of the generative cell in the pollen-tube, 

 each antherozoid being encircled by a spirally disposed ciliale 

 band which the author believes to be developed from the 

 fragments of a centrosome-like body. Mr. Webber observed 

 the discharge of the antherozoids from the pollen-tube, and 

 followed the passage of the motile male-gamete' into the 

 archegonium. " The entire antherozoid swims into the arche- 

 gonium, passing between the ruptured neck-cells." Several 

 antherozoids commonly enter each archegonium, but only one 

 of them takes part in fecundation. The method of antherozoid 

 formation in Zamia is regarded as similar to that in Cycas and 

 Ginkgo. 



Prof Campbell gave an account of some recent work on the 

 genus Lilira, a member of the Juncaginacere, and Prof. Coulter 

 read a paper on the life-history of A'aniinculus. The forma- 

 tion of endosperm prior to fertilisation, and other points of 

 interest in connection with reproduction and embryogeny, were 

 dealt with by these authors. 



Natural History, &c. 



On the chimney-shaped stomata of Holacantha Emoryi, by 

 Prof. Bessey. This prickly leafless shrub, known as the 

 " Sacred Thorn," "Crucifixion Thorn," iSic, is a native of the 

 arid regions of Southern Arizona. It possesses remarkable 

 breathing pores, which are evidently designed to enable the 

 plant to obtain carbon dioxide, while at the same time prevent- 

 ing the loss of water from its interior tissues. The epidermis is 

 extremely thick, and the stomata have long chimney-shaped 

 openings above them, terminating in hollow papillaf, which 

 project some distance above the surface. 



Prof Bessey also contributed a paper on the distribution 01 

 the native trees of Nebraska. 



