KNowunni:. 



rp.nKUAKv, 1VI2 



Aslr. Xticliriclitfii -ifi-ii cont.iiiis an intcrostiiif; note by 

 1^. IltTl/spninis', on tlic star Gruonib. J4 (K.A. O*" IJ"", N. Dec. 

 4J''-5). This is (1110 of the sovonlncn nearest stars, its parallax 

 bcin^; 0"-J,s, prupcr motion 2"'8(). inaKnitnde 7*7 ; it has an 

 eleventhinagnitndc companion, whose position ansle in 1,S64 

 was 5.V, distance J9"-.S: in IQOS these h.id changed to 57 . 

 iS"-7. The note sufjKcsts that this companion is the least 

 Inniinons star known to ns. being S-J niaKnitndes less than 

 onr sun at the same distance. If of the same snrface bright- 

 ness as our sun it would be comparable with Jupiter in size. 

 The principal star is of a yellow colom- and Ma spectrum : the 

 companion .agrees in colour, and doubtless in spectrum. It 

 will be long before enough of the orbit has been described to 

 determine the masses of the two stars. These may difi'er 

 nuich less than the luminosities, as in the cases of Sirius and 

 I'rocyon. 



SCH.MMASSE'S COMET.— The following cphcmeris of 

 this comet is from later elements, and therefore more 

 accurate than the one given in the "Face of the Sky." It 

 is for Paris midnight : — 



K.A. 



Feb. () ... 16 15 28 

 „ 10 ... 16 22 23 

 „ 14 ... 16 28 50 

 ., IS ... 16 34 46 



S.Dec. 



3° 51' 

 4 2 

 4 11 

 4 17 



K.A. 



S.Dec-. 



Feb. 22 ... 16 40 13 ... 4° 22 



.. 26 ... 16 45 S ... 4 25 



Mar. 1 ... 16 49 3(> ... 4 27 



5 ... 16 53 18 ... 4 27 



FKKATL'M LAST MONTH.— In the t.able of errors 

 of Encke's Comet, insert the word " iiiiniis" between 

 " Observed " and " Computed." 



BOTANY. 



Hy Professor F. Cavers, D.Sc, F.L.S. 



MUT.ATION IN SHEPHERDS PURSE.— From time to 

 time more or less strikingly abnormal forms have been 

 described in the widespread and very variable Shepherd's 

 Purse. For instance, in 1886 (Bot. Ccntralblatt. Hand 

 26, page 121), Wille pointed out that various earlier 

 observers had described abnormal forms of such Crucifers as 

 Wallflower and Charlock, which had more than the usual 

 number (two) of carpels, the number in some cases being as 

 great as six, but more often four. In some Crucifers there 

 are normally four carpels, and a four-valved fruit, c'.^>. 

 Holargidiuin and Tctrapoma. Wille had seen, in 1883, a 

 single Shepherd's Purse plant with three abnormal fruits 

 which had three, four, and six wings respectively. The 

 three-winged capsule had three valves, one complete and one 

 incomplete partition, and six rows of seeds; that with four 

 wings had four valves, two complete partitions, and eight rows 

 of seeds : while that with six wings consisted of an ordinary 

 two-valved fruit fused with a four-valved one, the stigmas 

 being separate. 



In 1900 iBot. Zcitiiiig, Band 581, Solms-Laubach described 

 a form which may be regarded as having arisen by nmtation 

 from the common Shepherd's Purse tCapsclla bursa- 

 pastorisK This new species iCapsclla heeneri^ had 

 appeared suddenly and spontaneously, and on being cultivated 

 for several years retained its characters, that is, bred true 

 from seed — it is an annu.al plant, like ordinary Shepherd's 

 Purse. Excepting for the structure of its fruit, C. hcciicri 

 resembles a variety of C. biirsa-pastoris with the radical 

 leaves pinnately cut. The capsule, however, is egg-shaped, 

 showing neither the flattening nor the two humps char.acteristic 

 of C. bursa pnsloris, and has at its base a short thick stalk. 

 Solms regards this new species as having arisen by mutation 

 from CapscUa bursa-pastoris, since its characters arc 

 constant and the fruit is widely different — sufliciently so. in 

 fact, to justify its being placed in a new genus. 



Shull (Proc. Int. Zool. Congress, Boston, 1907 ; published 

 in 1910— abstract in Hot. Ccntralblatt. Band 116. 19111 

 isolated four types or elementary species of Ca/ysclla bursa- 



pasloria differing in leaf characters, and foimd that in cross- 

 ing they behave as a Mendelian hybrid. Keciprocal crosses 

 were then made between C. Iiccucn and the simplest of the 

 four elementary species of C. biirsa-pastoris. In this way 

 four elementary species of C. Iiccficri were produced, the leaf 

 characters of these hybrids showing Mendelian ratios, but the 

 liccucri capsules appearing only in about one plant in two 

 hundred and twenty-three of the second generation Isec 

 Figure 2). 



Hlaringheni i/Jh//. Sci. France cl Bcli>.. 1<JI1> ha;- recently 

 described another new form of Capsclla. a single specimen of 

 which was found growing among abundant C. bnrsa-pastoris. 

 This history of this new species IC. viHHicri\ parallels that of 

 C. luxiicri, but C. vi)>uieri shows a variation of the capsules 

 in the opposite direction from that presented by C. Itccgcri. 

 Thegreat majority of the capsules have four valves, resembling 

 the two valves of C. bursa-pastoris and placed at right 

 angles to each other, but the number of valves varies from 

 two to eight. Counts of nearly ten thousand fruits showed : — 

 Two-valved, 2; three-valved, 81: four-valved, 8450; five- 

 valved, 301 ; six-valved, 288 : seven-valved. 24 ; eight-valved, 

 16. This new species is normally fasciated. and breeds true 

 to this character as well as to the high number of valves. 

 The leaves are almost entirely unlobed. 



Solms, Blaringhem, and Wille (whose paper appears to 

 have been overlooked by later writers on the subject, but has 

 been consulted by the present reviewer) lay stress on the fact 

 that several species of Cruciferae have four-winged capsules. 

 It is quite obvious that several species of Tctrapoma would, 

 if two-valved, be classified as species of Nasturtium : the 

 genus Ilolargidiuni, if two-valved. would be merged in 

 Draba ; while the Californian genus Tropidocarpon has one 

 species with two valves and one species with four. Moreover, 

 four-carpelled varieties, both cultivated and wild, are known 

 in such genera as Cheiranthus. Brassica. Isatis. and other 

 C'rucifers. Such instances as these, of the recurrence of 

 similar characters in more or less closely related species or 

 genera, support the view that variation is definite, or "ortho- 

 genetic," rather than entirely fortuitous. 



In reviewing Blaringhem 's paper. Shull {But. Gaz.. Jime. 

 I'll II remarks that mutations probably occur in Nature as 

 frequently, in proportion to the percentage of the seeds which 

 succeed in germinating and developing, as in experimental 

 cultures, but actual proof of such mutation is necessarily 

 wanting, as a rule. When a single individual of a hitherto 

 unknown type is seen to difl'er by some marked characteristic 

 from the associated typical individuals of the most closely 

 related species, the natural inference is that the non-typical 

 plant is a mutant. Such evidence is strengthened if the plant 

 is found to reproduce its characteristics in its ortspring. but 

 there remains the question of possible hybridisation ; and if 

 even that be satisfactorily ruled out, there is the possibility 

 that the form in question is not itself a mutant, but the oft"- 

 spring of a mutant, which appeared in some preceding genera- 

 tion. This last (juestion cannot, of course, be cleared up in 

 any case, but it is of no essential importance. 



BROWN FLAGELLATES AND BROWN ALGAE.— 

 Pascher has recently published two interesting papers ( Bcr. d. 

 dcutsch. bot. Gcs., 1911) de.iling with Brown Fl.igcllates and 

 the relations of these to the Brown .-\lgae. 



In the first paper he gives a short account of two new- 

 genera of Brown Flagellates. Cryptochrysis. which was 

 only observed in the motile state, resembles other Flagellata 

 in having no cell-wall and in dividing by a plane parallel to 

 the long axis of the body, which is an ellijisoid inas^ of 

 protoplasm : the broader notched anterior end bears two 

 whip-like flagella. and the protoplast contains two brown 

 pigment-bodies. Protoclirysis is also ellipsoid but curved 

 and bean-shaped, with two flagella in.serted at the middle of 

 the concave side ; the chrom.itophores, two in mnnbcr, may 

 be reddish or blui.sh-green in.ste.ad of brown : division occurs 

 In a motionless condition, the cells rounding olV, becoming 

 surrounded by a swollen membrane and dividing into colonies 

 of from four to eight cells. 



