482 PRACTICAL BOTANY 



sections. It will be further observed that the peripheral tissue is 

 similar to the central, with the exception of colour and consist- 

 ency. Small masses of tissue of the ovary of the Grass may 

 sometimes be found embedded in the sclerotium. 



Treat a section with chlor-zinc-iodine : the cell- walls will 

 stain a faint yellow, and this colour is not changed even after 

 some hours' treatment with the reagent (fungal cellulose). 



III. Set sclerotia to germinate, half buried in moist clean sand, 

 at a moderate temperature : this will succeed best in spring or 

 early summer, since even if the cultures be started at other seasons, 

 under most favourable conditions, the sclerotia will (with very few 

 exceptions) undergo no change till the proper season comes round. 

 When germination begins, the peripheral tissue will be broken 

 through at one or more points by the swelling of a light-coloured 

 mass within : this grows quickly, so as to form a stroma, which 

 consists when mature of an erect cylindrical stalk one inch or 

 less in length, and a spherical head. Examine the latter with a 

 lens : it is when mature of a purplish colour, and marked with 

 numerous projecting dots. 



IV. Cut transverse sections of a sclerotium which has already 

 germinated, and in such a way as to traverse the base of a mature 

 stroma : mount in glycerine, and observe 



1. That the store of oil, &c., in the sclerotium is much reduced, 

 and the whole tissue soft and apparently exhausted. 



2. That the tissue of the stalk is of a distinctly hyphal 

 character, the hyphse being arranged parallel one to another, and 

 septate. 



3. That at the base of the stalk the hyphse appear to have 

 originated from the pseudo -parenchyma of the sclerotium. 



V. Cut median longitudinal sections of the mature head 

 of a stroma, and including the upper part of the stalk : mount 

 as before, and examine under a low power : observe 



1. The upper part of the stalk showing the same structure as 

 the base. 



2. The semi-lunar section of the head, inserted upon it. 



3. The numerous flask-shaped perithecia embedded in its 

 mass, each having a slight papillose projection of the surface 

 opposite it : these have already been observed from outside. 



