CARBOHYDRATES OF THALLOPHYTA AND BRYOPHYTA 59 



Busolt (1913) has shown that sap from French beans 

 yields a considerable amount of mannitol when kept for a 

 week, though none was detected in fresh sap or in sap kept 

 for a week after sterilization while fresh. Cauliflower heads, 

 on the other hand, afford mannitol when quite fresh, though 

 it is possible that it may have been formed during evapora- 

 tion of the juice. This change, either bacterial or enzymic, 

 casts doubt on the reality of presence of mannitol in brown 

 algae. It is not impossible that in them trehalose may 

 occur instead of sucrose, being an intermediate step in the 

 formation of laminar in. The identification of trehalose by 

 any means other than by obtaining it in a pure crystalline 

 condition is very uncertain. Its presence could of course 

 be deduced by quantitative methods. This suggestion as 

 to the occurrence and role of trehalose is, it must be re- 

 membered, purely speculative. 



CARBOHYDRATES OF THE BRYOPHYTA. 

 With regard to other holophytic members of the Thallo- 

 phyta and Bryophyta little quantitative work appears to 

 have been done, but the presence of glucose, fructose, 

 sucrose, and starch, has been demonstrated in many cases. 

 Marchal (1906) has investigated the distribution of starch 

 in this group, and has recorded its absence from a con- 

 siderable number of mosses. From these maltose is also 

 absent. Mason * (1915) has noted the absence of starch 

 from the leaves of Thuidium tamariscinum and Sphagnum 

 cymbifolium. Marchal, however, found it in the young 

 leaves of the former, and its presence in the upper part of 

 the stem of the latter was demonstrated by Mason. As 

 additional evidence for the presence of sucrose hi certain 

 mosses, Mason has shown that invertase is present in the 



* The publication of Mr. Mason's results was delayed for a year 

 owing to his departure for France on active service. 



