ROTA ANGLICA 67 



usually observed to be in this condition, but in the case o£ older cells, 

 and almost always in very long individuals, it was frequently com- 

 pletely divided in the middle, the nucleus then being in a central posi- 

 tion between the two half-chloroplasts (C, D). This division of the 

 chloroplast appears to be preliminary to cell-division, but exactly how 

 long the condition jx^rsists before the cell actually divides, or whether 

 the divided chloroplast is to be considered a normal feature of the 

 adult cell cannot definitely be stated. 



W. & G. S. West (in Journ. R. M. S. 1896, t. iii. fig. 2Sa') 

 have given a figure of lio^a obtusa, var, montana showing the chloro- 

 plast completely divided in the middle, but no mention of this is 

 made in the test. Liitkemiiller* also figures an example of this 

 condition in Hoya obtusa^ and sa3^s : " kommen aber auch oft genug 

 Exemplare des CI. ohfusum zur Beobachtung deren Chlorophoren in 

 der Zellmitte nicht einen seitlichen Ausschnitt, sondern eine voll- 

 standige Unterbrechung zeigen." 



As such individuals might be mistaken by a beginner for a species 

 of Clostermm, it should be noted that in the latter genus division of 

 the chloroplast into two takes place very early, and is usually com- 

 pleted before the young daughter-cells have separated. The greatly 

 delayed division of the chloroplast is thus very characteristic of the 

 genus Boya. In B. camhrica — which has been found several times in 

 some marshes at Bearwood, near Birmingham — such cells with two 

 chloroplasts were only rarely seen, in fact the condition was observed 

 only in cells obviously soon going to divide. 



Liitkemiiller (/. c.) states that some species of Glosterium are known 

 in which *'das Chlorophor in der Zellmitte der Kegel nach nicht unter- 

 brochen sondern nur seitlich ausgeschnitten ist {CI. Linea^ CI. acu^ 

 turn).'''' But W. & Gr. S. West's figures {Desmidiacece, i. t. xxiii.) of 

 CI. Linea Perty [=(7Z. acutum var. Linea (Perty) W. & G-. S. 

 West], and CI. acutum (Lyngb.) Breb. show two distinct chloroplasts, 

 and it may be that Liitkemiiller's statement was based upon obser- 

 vation of abnormal specimens. CI. acutum was found by the present 

 wa-iter in a small pond near Birmingham, in 1918, but the cells always 

 showed two chloroplasts. 



Ver}^ striking in B. anglica is the fact that the distal extremities 

 of the chloroplast are always markedly concave, and at each end of 

 the cell there is a conspicuous vacuole in which, however, no granules 

 of an}^ sort were ever seen (see A-D). These characters at once 

 distinguish the present species from the three previously described 

 species of Boy a. W. & Gr. S. West {op. clt. 106) considered that 

 the rounded ends of the chloroplast, and absence of terminal vacuoles, 

 to be amongst the most characteristic features of the genus Boya^ 

 but such characters cannot now be regarded as of generic importance. 

 With regard to the presence of apical vacuoles in B. anglica it is 

 interesting to note that Liitkemiiller (/. c.) has described a species of 

 Clostermm {CI. car?iiolicum) in which terminal vacuoles are absent, 



* "Desmidiaceen aus der Umgebung des Millstiittereees in Karnten," op. cit, 

 1. 61 (1900). 



r2 



